High-adhesion, high-edge coverage powder coating polyester resin for coating of metal cutting parts, and method for preparing the same, and powder coating

Abstract

This invention provides a polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts, its preparation method, and the powder coating. The raw materials include 15-18 parts neopentyl glycol, 20-25 parts terephthalic acid, 2-4 parts adipic acid, 0.3-0.5 parts trimethylolpropane, 10-13 parts isophthalic acid, 0.05 parts esterification catalyst, 0.5 parts antioxidant, 0.2 parts silane coupling agent, 0.1 parts charge adjuster, and 0.04 parts curing accelerator. The prepared polyester resin has high viscosity but does not gel, measuring 3500-4000 mPa·s / 230℃ using a Brookfield cone-plate viscometer. When preparing the final powder coating product, it effectively achieves high strength performance with high edge coverage, and effectively improves the protective and decorative properties and adhesion of the powder coating.

Description

Technical Field

[0001] This invention belongs to the field of powder coating technology, specifically relating to polyester resin for high adhesion and high edge coverage powder coating of metal cutting parts, its preparation method, and powder coating. The polyester resin is used to prepare 93 / 7 outdoor TGIC type powder coating. Background Technology

[0002] Powder coatings, as a new type of pollution-free coating, have been widely used for the decoration of metal and other surfaces. Powder coatings are solid powdered synthetic resin coatings composed of solid resin, pigments, fillers, and additives. Unlike ordinary solvent-based and water-based coatings, its dispersion medium is not solvent or water, but air. It features solvent-free pollution, 100% film formation, and low energy consumption. Different workpieces have different requirements; therefore, the selection of materials and corresponding coating preparation schemes should be specifically combined with the requirements of different workpieces when preparing and using thermosetting powder coatings to meet the coating requirements.

[0003] Powder coatings are widely used on industrial metal cutting parts, which have sharp edges and many corners. Therefore, high requirements are placed on the coating protection and decoration of these cutting edges. Thus, great importance is attached to the use of raw materials and the design of powder coating formulations.

[0004] Outdoor 93 / 7 type TGIC powder coatings are widely used for spraying and decorating cut metal parts in outdoor industrial applications. They typically require cross-linking and curing of polyester resin and TGIC curing agent to form a film. However, due to the material reactivity and viscosity of conventional 93 / 7 type TGIC polyester resins, the cut areas are prone to thermal shrinkage during the powder coating curing process, leading to issues such as exposed substrate and broken lines on the coated workpiece. Currently available high-viscosity polyester resins have a viscosity of 8000-9000 mPa·s at 200℃, meaning that powder coatings prepared with these resins cannot provide good coverage, protection, and decoration at cut areas. To address this, liquid paint repair or secondary spraying is usually used, which is time-consuming, labor-intensive, polluting, and wasteful of resources.

[0005] Therefore, it is of great significance to develop a polyester resin for powder coating of industrial metal cutting parts with high adhesion and high edge coverage. Summary of the Invention

[0006] The purpose of this invention is to provide a polyester resin for high adhesion and high edge coverage powder coating of metal cutting parts and its preparation method. It is obtained by polymerization of neopentyl glycol, terephthalic acid, adipic acid, trimethylolpropane, isophthalic acid, silane coupling agent and charge modifier. It has high viscosity, fast reaction and high adhesion strength.

[0007] Another objective of this invention is to provide a powder coating prepared using the aforementioned high-adhesion, high-edge-coverage powder coating polyester resin for metal cutting parts. The powder coating product can effectively achieve the purpose of high adhesion strength, protection, and decoration for industrial metal cutting parts under high edge coverage, and can effectively protect industrial metal cutting parts from external corrosion.

[0008] The specific technical solution of this invention is as follows:

[0009] A polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts comprises the following raw materials in parts by weight:

[0010] Neopentyl glycol 15-18 parts

[0011] 20-25 parts terephthalic acid

[0012] 2-4 parts adipic acid

[0013] 0.3-0.5 parts of trimethylolpropane

[0014] 10-13 parts of isophthalic acid

[0015] 0.05 parts of esterification catalyst

[0016] 0.5 parts antioxidant

[0017] 0.2 parts of silane coupling agent

[0018] 0.1 parts of charge adjuster

[0019] 0.04 parts of curing accelerator.

[0020] Preferably, the polyester resin for high-adhesion, high-edge-coverage powder coating of the metal cut parts comprises the following raw materials in parts by weight:

[0021] 16 parts of neopentyl glycol

[0022] 22 parts of terephthalic acid

[0023] Adipic acid 2.7 parts

[0024] 0.4 parts of trimethylolpropane

[0025] 11 parts of isophthalic acid

[0026] 0.05 parts of esterification catalyst

[0027] 0.5 parts antioxidant

[0028] 0.2 parts of silane coupling agent

[0029] 0.1 parts of charge adjuster

[0030] 0.04 parts of curing accelerator.

[0031] The esterification catalyst raw material is monobutyltin oxide.

[0032] The antioxidants include BASF B900 compound antioxidants.

[0033] The charge modifier is SA2483 from Liuan Jietongda. The polar fatty acid esters used as charge-carrying agents in powder coatings are mainly solid products represented by ethylene glycol esters or sorbitol esters of stearic acid or other fatty acids, with a melting point range of about 60°C.

[0034] The silane coupling agent is PTN101 from Suzhou Partner Environmental New Materials Co., Ltd., with the following structure: Y-R-Si-X3. Its composition contains Y representing an organic functional group, R representing an alkylene group, and X representing a hydrolyzable group. It acts at the interface between inorganic materials and organic resins (especially thermosetting resins) to build a strong "molecular bridge," binding and coupling two completely different materials, thereby greatly improving the dry and wet mechanical strength and electrical properties of various resin-based composite materials.

[0035] The curing accelerator is benzyltriethylammonium chloride.

[0036] The present invention provides a method for preparing a polyester resin for a high-adhesion, high-edge-coverage powder coating for metal cutting parts, comprising the following steps:

[0037] 1) Take the prescribed amounts of neopentyl glycol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amount of esterification catalyst into the reaction vessel. Heat to 200℃ and keep warm until the acid value is 5-10 mg KOH / g.

[0038] 2) Add antioxidant and stir to mix well;

[0039] 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amounts of silane coupling agent and charge adjuster, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 3500-4000 mPa.s / 230℃.

[0040] 4) Cool down to 185℃, add curing accelerator, stir evenly; after cooling, the product is ready.

[0041] In step 1), the temperature is raised to 200°C at a heating rate of 20°C / h;

[0042] The heat preservation mentioned in step 1) refers to heating to 200℃ and maintaining that temperature for 2 hours;

[0043] After adding the antioxidant in step 2), stir at 200°C for 30 minutes until homogeneous.

[0044] In step 4), the mixing time is 30 minutes.

[0045] The powder coating provided by the present invention is prepared using the polyester resin for high adhesion and high edge coverage powder coating of metal cutting parts described above;

[0046] The powder coating comprises the following raw materials in parts by weight:

[0047] 539.4 parts of polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts.

[0048] TGIC curing agent 40.6 parts

[0049] 8 parts carbon black

[0050] 388 portions of barium sulfate

[0051] 10 parts leveling agent

[0052] 5 portions of benzoin

[0053] 3 parts of 701B brightening agent.

[0054] The powder coating prepared using the polyester resin for high adhesion and high edge coverage powder coating of the above-mentioned metal cutting parts is used as an outdoor TGIC-cured powder coating of category 93 / 7.

[0055] The inventors discovered that when the viscosity of the synthesized polyester is measured at 3500-4000 mPa·s at 230°C, it can meet the requirements for edge shrinkage and abrasion resistance adhesion without gelling during coating preparation. The high-adhesion, high-edge-coverage powder coating polyester resin provided by this invention is obtained by polymerization of neopentyl glycol, terephthalic acid, adipic acid, trimethylolpropane, isophthalic acid, silane coupling agent, and charge modifier. Measurements showed that the polyester resin prepared with this acid alcohol had high viscosity but did not gel, measuring 3500-4000 mPa·s / 230℃ using a Brookfield cone-plate viscometer. Adding trimethylolpropane during synthesis helped the synthesized polyester exhibit better reactivity and higher viscosity, resulting in better curing performance and edge coverage during crosslinking with the curing agent. Furthermore, introducing a small amount of silane coupling agent and charge modifier in the early stage of the polymerization vacuum reaction allowed the hydroxyl groups generated from the hydrolysis of the X groups in the silane coupling agent to undergo condensation reactions with the incompletely reacted hydroxyl groups in the early stage of polyester resin synthesis, forming chemical bonds. This enabled the coating to adhere well to the workpiece surface during the preparation of thermosetting powder coatings. The addition of the charge modifier allowed the polar fatty acid groups to undergo condensation reactions with the carboxyl groups of the polyester resin through vacuum polymerization. Combined with the high viscosity and high activity of the polyester resin, this effectively achieved high strength performance with high edge coverage in the preparation of finished powder coating products, significantly improving the protective and decorative properties and adhesion of the powder coating. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0058] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0059] The esterification catalyst used in this invention is monobutyltin oxide.

[0060] The antioxidants include BASF B900 compound antioxidants.

[0061] The charge modifier is SA2483 from Liuan Jietongda.

[0062] The silane coupling agent is PTN101 from Suzhou Partner Environmental New Materials Co., Ltd.

[0063] Example 1

[0064] A polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts comprises the following raw materials in parts by weight:

[0065] 16 parts of neopentyl glycol

[0066] 22 parts of terephthalic acid

[0067] Adipic acid 2.7 parts

[0068] 0.4 parts of trimethylolpropane

[0069] 11 parts of isophthalic acid

[0070] 0.05 parts of esterification catalyst

[0071] 0.5 parts antioxidant

[0072] 0.2 parts of silane coupling agent

[0073] 0.1 parts of charge adjuster

[0074] 0.04 parts of curing accelerator.

[0075] 1) Take the prescribed amounts of neopentyl glycol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amounts of monobutyltin oxide. Heat at a rate of 20°C / h to 200°C and maintain for 2 hours. Measure the acid value until it reaches 5-10 mg KOH / g.

[0076] 2) Add the antioxidant B900 and stir at 200°C for 30 minutes until homogeneous.

[0077] 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amounts of silane coupling agent and charge adjuster, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 3500-4000 mPa.s / 230℃.

[0078] 4) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0079] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0080] The polyester resin prepared in this embodiment was tested and found to have an acid value of 33.2 mg KOH / g and a viscosity of 3850 mPa.s / 230℃.

[0081] Example 2

[0082] A polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts comprises the following raw materials in parts by weight:

[0083] 17 parts of neopentyl glycol

[0084] 22 parts of terephthalic acid

[0085] Adipic acid 2.7 parts

[0086] 0.35 parts of trimethylolpropane

[0087] 11 parts of isophthalic acid

[0088] 0.05 parts of esterification catalyst

[0089] 0.5 parts antioxidant

[0090] 0.2 parts of silane coupling agent

[0091] 0.1 parts of charge adjuster

[0092] 0.04 parts of curing accelerator.

[0093] The preparation method of the polyester resin for high adhesion and high edge coverage powder coating described in this embodiment is the same as in Embodiment 1;

[0094] The polyester resin prepared in this embodiment was tested and found to have an acid value of 31.7 mg KOH / g and a viscosity of 3640 mPa.s / 230℃.

[0095] Example 3

[0096] A polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts comprises the following raw materials in parts by weight:

[0097] 16 parts of neopentyl glycol

[0098] 20 parts terephthalic acid

[0099] Adipic acid 2.7 parts

[0100] 0.4 parts of trimethylolpropane

[0101] 13 parts of isophthalic acid

[0102] 0.05 parts of esterification catalyst

[0103] 0.5 parts antioxidant

[0104] 0.2 parts of silane coupling agent

[0105] 0.1 parts of charge adjuster

[0106] 0.04 parts of curing accelerator.

[0107] The method for preparing polyester resin for high adhesion and high edge coverage powder coating described in this embodiment is the same as in Embodiment 1.

[0108] The polyester resin prepared in this embodiment was tested and found to have an acid value of 34.5 mg KOH / g and a viscosity of 3540 mPa.s / 230℃.

[0109] Example 4

[0110] A polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts comprises the following raw materials in parts by weight:

[0111] 15 parts of neopentyl glycol

[0112] 22 parts of terephthalic acid

[0113] Adipic acid 2.7 parts

[0114] 0.5 parts of trimethylolpropane

[0115] 11 parts of isophthalic acid

[0116] 0.05 parts of esterification catalyst

[0117] 0.5 parts antioxidant

[0118] 0.2 parts of silane coupling agent

[0119] 0.1 parts of charge adjuster

[0120] 0.04 parts of curing accelerator.

[0121] The method for preparing polyester resin for high adhesion and high edge coverage powder coating described in this embodiment is the same as in Embodiment 1.

[0122] The polyester resin prepared in this embodiment was tested and found to have an acid value of 32.6 mg KOH / g and a viscosity of 3940 mPa.s / 230℃.

[0123] Comparative Example 1

[0124] A polyester resin comprising the following raw materials in parts by weight:

[0125] 22 parts of terephthalic acid

[0126] Adipic acid 2.7 parts

[0127] 14.1 parts of trimethylolpropane

[0128] 11 parts of isophthalic acid

[0129] 0.05 parts of esterification catalyst

[0130] 0.5 parts antioxidant

[0131] 0.2 parts of silane coupling agent

[0132] 0.1 parts of charge adjuster

[0133] 0.04 parts of curing accelerator.

[0134] The method for using polyester resin in coatings described in this comparative example includes the following steps:

[0135] 1) Take the prescribed amount of trimethylolpropane and terephthalic acid, mix them, and add the prescribed amount of esterification catalyst monobutyltin oxide. Heat at a rate of 10℃ / h to 200℃ and maintain for 2 hours. Measure the acid value until it reaches 5-8 mgKOH / g.

[0136] 2) Add the antioxidant B900 and stir at 200°C for 30 minutes until homogeneous.

[0137] 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 220℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amounts of silane coupling agent and charge adjuster, cool to 180℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 5500-6000 mPa.s / 230℃.

[0138] 4) Cool down to 170℃, add curing accelerator, and stir evenly for 30 minutes.

[0139] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0140] Compared with Example 1, the raw material composition used to prepare the polyester resin in this comparative example does not contain neopentyl glycol, but the amount of trimethylolpropane is 14.2 parts, and the mass parts of the other raw materials remain unchanged. Since trimethylolpropane has high activity, the initial heating rate is adjusted to 10℃ / h, and the heating and maintenance temperature in step 3) is reduced to 220℃, the vacuum temperature is reduced to 180℃, and the temperature is reduced to 170℃ in step 4).

[0141] The polyester resin prepared in this embodiment was tested and found to have an acid value of 32.2 mg KOH / g and a viscosity of 5740 mPa.s / 230℃.

[0142] Comparative Example 2

[0143] A polyester resin comprising the following raw materials in parts by weight:

[0144] 16 parts of neopentyl glycol

[0145] Adipic acid 2.7 parts

[0146] 0.4 parts of trimethylolpropane

[0147] 33 parts of isophthalic acid

[0148] 0.05 parts of esterification catalyst

[0149] 0.5 parts antioxidant

[0150] 0.2 parts of silane coupling agent

[0151] 0.1 parts of charge adjuster

[0152] 0.04 parts of curing accelerator.

[0153] The method for the polyester resin described in this comparative example includes the following steps:

[0154] 1) Take the prescribed amount of neopentyl glycol, trimethylolpropane and 22 parts of isophthalic acid, mix them together and add the prescribed amount of monobutyltin oxide. Heat at a rate of 20℃ / h to 200℃ and maintain for 2 hours. Measure the acid value until it is 5-10 mg KOH / g.

[0155] 2) Add antioxidant B900 and stir at 200℃ for 30 minutes until homogeneous.

[0156] 4) Add the prescribed amount of adipic acid and 11 parts of isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amount of silane coupling agent and charge adjuster, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 1500-2000 mPa.s / 230℃.

[0157] 5) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0158] 6) Cool the above-mentioned compound, and then compress and crush it to obtain the product.

[0159] Compared with Example 1, the raw material composition used to prepare the polyester resin in this comparative example does not contain terephthalic acid, but the amount of isophthalic acid is 33 parts, and the mass parts of the other raw materials remain unchanged.

[0160] The polyester resin prepared in this embodiment was tested and found to have an acid value of 34.5 mg KOH / g and a viscosity of 1780 mPa.s / 230℃.

[0161] Comparative Example 3

[0162] A polyester resin comprising the following raw materials in parts by weight:

[0163] 16 parts of neopentyl glycol

[0164] 22 parts of terephthalic acid

[0165] 0.4 parts of trimethylolpropane

[0166] 12.1 parts of isophthalic acid

[0167] 0.05 parts of esterification catalyst

[0168] 0.5 parts antioxidant

[0169] 0.2 parts of silane coupling agent

[0170] 0.1 parts of charge adjuster

[0171] 0.04 parts of curing accelerator.

[0172] The method for preparing polyester resin described in this embodiment includes the following steps:

[0173] 1) Take the prescribed amounts of neopentyl glycol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amounts of monobutyltin oxide. Heat at a rate of 20℃ / h to 200℃ and maintain for 2 hours. Measure the acid value until it reaches 5-10 mg KOH / g.

[0174] 2) Add the antioxidant B900 and stir at 200°C for 30 minutes until homogeneous.

[0175] 3) Add the prescribed amount of isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amount of silane coupling agent and charge adjuster, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 4500-5000 mPa.s / 230℃.

[0176] 4) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0177] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0178] Compared with Example 1, the raw material composition used to prepare the polyester resin in this comparative example does not contain adipic acid, but the amount of isophthalic acid is 12.1 parts, and the mass parts of the other raw materials remain unchanged.

[0179] The polyester resin prepared in this embodiment was tested and found to have an acid value of 33.8 mg KOH / g and a viscosity of 4610 mPa.s / 230℃.

[0180] Comparative Example 4

[0181] A polyester resin comprising the following raw materials in parts by weight:

[0182] Neopentyl glycol 16.3 parts

[0183] 22 parts of terephthalic acid

[0184] Adipic acid 2.7 parts

[0185] 11 parts of isophthalic acid

[0186] 0.05 parts of esterification catalyst

[0187] 0.5 parts antioxidant

[0188] 0.2 parts of silane coupling agent

[0189] 0.1 parts of charge adjuster

[0190] 0.04 parts of curing accelerator.

[0191] The comparative method for preparing polyester resin includes the following steps:

[0192] 1) Take the prescribed amount of neopentyl glycol and terephthalic acid, mix them together, and add the prescribed amount of monobutyltin oxide. Heat at a rate of 20℃ / h to 200℃ and maintain for 2 hours. Measure the acid value until it reaches 5-10 mg KOH / g.

[0193] 2) Add the antioxidant B900 and stir at 200°C for 30 minutes until homogeneous.

[0194] 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amounts of silane coupling agent and charge adjuster, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 3000-3500 mPa.s / 200℃.

[0195] 4) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0196] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0197] Compared with Example 1, the raw material composition used to prepare the polyester resin in this comparative example does not contain trimethylolpropane, and the amount of neopentyl glycol is 16.3 parts, while the mass parts of the other raw materials remain unchanged.

[0198] The acid value of the polyester resin prepared in this comparative example was tested to be 31.4 mg KOH / g, and the viscosity was 3420 mPa.s / 200℃.

[0199] Comparative Example 5

[0200] A polyester resin comprising the following raw materials in parts by weight:

[0201] 16 parts of neopentyl glycol

[0202] 22 parts of terephthalic acid

[0203] 12.4 parts adipic acid

[0204] 0.4 parts of trimethylolpropane

[0205] 0.05 parts of esterification catalyst

[0206] 0.5 parts antioxidant

[0207] 0.2 parts of silane coupling agent

[0208] 0.1 parts of charge adjuster

[0209] 0.04 parts of curing accelerator.

[0210] The method for preparing a polyester resin for high adhesion and high edge coverage powder coating as described in this comparative example includes the following steps:

[0211] 1) Take the prescribed amount of neopentyl glycol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amount of monobutyltin oxide. Heat at a rate of 20°C / h to 200°C and maintain for 2 hours. Measure the acid value until it reaches 5-10 mg KOH / g.

[0212] 2) Add antioxidant B900 and stir at 200℃ for 30 minutes until homogeneous.

[0213] 3) Add the amount of adipic acid specified in the formula, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the amount of silane coupling agent and charge adjuster specified in the formula, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 2000-2500 mPa.s / 230℃.

[0214] 4) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0215] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0216] Compared with Example 1, the raw material composition used to prepare the polyester resin in this comparative example does not contain isophthalic acid, but the amount of adipic acid is 12.4 parts, and the mass parts of the other raw materials remain unchanged.

[0217] The acid value of the polyester resin prepared in this comparative example was tested to be 34.1 mg KOH / g, and the viscosity was 2360 mPa.s / 230℃.

[0218] Comparative Example 6

[0219] A polyester resin comprising the following raw materials in parts by weight:

[0220] 10 parts of neopentyl glycol

[0221] 1.2 parts ethylene glycol

[0222] 3.5 parts of 2-methyl-1,3-propanediol

[0223] 22 parts of terephthalic acid

[0224] Adipic acid 2.7 parts

[0225] 0.4 parts of trimethylolpropane

[0226] 11 parts of isophthalic acid

[0227] 0.05 parts of esterification catalyst

[0228] 0.5 parts antioxidant

[0229] 0.2 parts of silane coupling agent

[0230] 0.1 parts of charge adjuster

[0231] 0.04 parts of curing accelerator.

[0232] The method for using polyester resin in coatings described in this comparative example includes the following steps:

[0233] 1) Take the prescribed amounts of neopentyl glycol, ethylene glycol, 2-methyl-1,3-propanediol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amount of esterification catalyst monobutyltin oxide. Heat at a rate of 20℃ / h to 200℃ and maintain for 2 hours. Measure the acid value until it reaches 5-8 mg KOH / g.

[0234] 2) Add the antioxidant B900 and stir at 200°C for 30 minutes until homogeneous.

[0235] 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amounts of silane coupling agent and charge adjuster, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 2500-3000 mPa.s / 200℃.

[0236] 4) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0237] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0238] Compared with Example 1, the raw material composition used to prepare the polyester resin in this comparative example is that some diethanol and 2-methyl-1,3-propanediol are used to replace part of neopentyl glycol, while the mass fractions of the remaining raw materials remain unchanged.

[0239] The polyester resin prepared in this embodiment was tested and found to have an acid value of 31.6 mg KOH / g and a viscosity of 2670 mPa.s / 200℃.

[0240] Comparative Example 7

[0241] A polyester resin comprising the following raw materials in parts by weight:

[0242] 16 parts of neopentyl glycol

[0243] 22 parts of terephthalic acid

[0244] Adipic acid 2.7 parts

[0245] 0.4 parts of trimethylolpropane

[0246] 11 parts of isophthalic acid

[0247] 0.05 parts of esterification catalyst

[0248] 0.5 parts antioxidant

[0249] 0.1 parts of charge adjuster

[0250] 0.04 parts of curing accelerator.

[0251] The method for preparing polyester resin for powder coating described in this comparative example includes the following steps:

[0252] 1) Take the prescribed amounts of neopentyl glycol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amounts of monobutyltin oxide. Heat at a rate of 20℃ / h to 200℃ and maintain for 2 hours. Measure the acid value until it reaches 5-10 mg KOH / g.

[0253] 2) Add antioxidant B900 and stir at 200℃ for 30 minutes until homogeneous.

[0254] 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amount of charge adjuster, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 3500-4000 mPa.s / 230℃.

[0255] 4) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0256] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0257] The raw material composition used to prepare the polyester resin in this comparative example is different from that in Example 1. It does not contain silane coupling agent, and the mass fractions of the other raw materials remain unchanged.

[0258] The acid value of the polyester resin prepared in this comparative example was tested to be 32.2 mg KOH / g, and the viscosity was 3860 mPa.s / 230℃.

[0259] Comparative Example 8

[0260] A polyester resin comprising the following raw materials in parts by weight:

[0261] 16 parts of neopentyl glycol

[0262] 22 parts of terephthalic acid

[0263] Adipic acid 2.7 parts

[0264] 0.4 parts of trimethylolpropane

[0265] 11 parts of isophthalic acid

[0266] 0.05 parts of esterification catalyst

[0267] 0.5 parts antioxidant

[0268] 0.1 parts of charge adjuster

[0269] 0.2 parts of titanate coupling agent

[0270] 0.04 parts of curing accelerator;

[0271] The titanate coupling agent used is titanate coupling agent 109 from Jinan Rongzheng Chemical Co., Ltd.

[0272] The method for preparing polyester resin for powder coating described in this comparative example includes the following steps:

[0273] 1) Take the prescribed amounts of neopentyl glycol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amounts of monobutyltin oxide. Heat at a rate of 20℃ / h to 200℃ and maintain for 2 hours. Measure the acid value until it reaches 5-10 mg KOH / g.

[0274] 2) Add antioxidant B900 and stir at 200℃ for 30 minutes until homogeneous.

[0275] 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amounts of charge adjuster and titanate coupling agent, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 6500-7000 mPa.s / 230℃.

[0276] 4) Cool down to 185℃, add curing accelerator, and stir evenly for 30 minutes.

[0277] 5) Cool the above-mentioned compound, and then press and crush it to obtain the product.

[0278] Compared with Example 1, the raw material composition used to prepare the polyester resin in this comparative example is that the silane coupling agent is changed to another type of titanate coupling agent, while the mass fraction of the remaining raw materials remains unchanged.

[0279] The acid value of the polyester resin prepared in this comparative example was tested to be 33.5 mg KOH / g, and the viscosity was 6860 mPa.s / 230℃.

[0280] Comparative Example 9

[0281] A polyester resin for high adhesion and high edge coverage powder coatings comprises the following raw materials in parts by weight:

[0282] 16 parts of neopentyl glycol

[0283] 22 parts of terephthalic acid

[0284] Adipic acid 2.7 parts

[0285] 0.4 parts of trimethylolpropane

[0286] 11 parts of isophthalic acid

[0287] 0.05 parts of esterification catalyst

[0288] 0.5 parts antioxidant

[0289] 0.2 parts of silane coupling agent

[0290] 0.04 parts of curing accelerator.

[0291] The raw material composition used to prepare the polyester resin in this comparative example is different from that in Example 1, without the addition of a charge adjuster.

[0292] The acid value of the polyester resin prepared in this comparative example was tested to be 34.1 mg KOH / g, and the viscosity was 3800 mPa.s / 230℃.

[0293] The polyester resins obtained in Examples 1-4 and Comparative Examples 1-9 of this invention were used to prepare outdoor 93 / 7 type TGIC cured powder coatings according to the following composition:

[0294] 539.4 parts of polyester resin

[0295] TGIC curing agent 40.6 parts

[0296] 8 parts carbon black

[0297] 388 portions of barium sulfate

[0298] 10 parts leveling agent

[0299] 5 portions of benzoin

[0300] 3 parts of 701B brightening agent.

[0301] The leveling agent used was GLP588 from Ningbo Nanhai Chemical.

[0302] In the prior art, a commercially available ordinary 93 / 7 type TGIC curing powder coating polyester resin (acid value of 32.5 mg KOH / g, viscosity of 8860 mPa.s / 200℃) was used instead of the polyester resin described in this invention as Comparative Example 10.

[0303] The powder coating is mixed according to the formula, extruded, pressed, crushed, and sieved to obtain the finished powder coating. The prepared sample is cut along the center of the sample using the same 1.2 mm metal cutting disc. The sample is then uniformly sprayed onto the surface-treated cut metal plate and placed in an oven for baking at 200℃ for 10 minutes to form a film, thus completing the coating.

[0304] After observing the edge coverage of the samples under the same conditions, all the coated sample edges were further rubbed with the same force (approximately 1000g) for 10 rounds using commercially available 240-grit sandpaper, and the degree of wear was observed; the results are shown in Table 1. This invention uses powder coatings made of polyester resin from each embodiment and comparative example. Except for the polyester resin, the other components and contents are completely identical, and the testing methods are also the same.

[0305] Table 1 Test results of coatings in each example and comparative example

[0306]

[0307] As can be seen from the experimental data in Table 1 above, the polyester resin prepared by the present invention has good coating strength and adhesion performance under the same test conditions while ensuring high coverage, and does not gel, making it suitable for spray coating decoration of industrial metal cutting parts at present. When other alcohols are used to replace neopentyl glycol, the viscosity of the synthesized polyester is generally low, failing to meet the synthesis requirements. Because neopentyl glycol has a unique highly branched structure, combined with trimethylolpropane (TMAP), a trifunctional group, the synthesized polyester can achieve a higher viscosity without gelation. Silane coupling agents are organosilicon compounds with a special structure, possessing reactive groups that can bind to metals and reactive groups that can bind to resins. They can effectively graft the required groups into the synthesized carboxyl-terminated polyester and increase the adhesion strength to the metal substrate. Compared with Comparative Example 7 (without silane coupling agent) and Comparative Example 8 (with other types of titanate coupling agents), the former shows more severe wear, while the latter, due to the influence of the titanate structure, undergoes rapid transesterification when added to the polymer, resulting in an excessively high viscosity of the synthesized polyester. During the extrusion process in the extruder, gelation occurs, ultimately failing to yield the finished coating. Meanwhile, charge modifiers containing polar fatty acid groups are also added to the synthetic polyester resin to change the surface resistivity of the powder coating. When applied to powder coating, in addition to improving the electrical properties, the prepared powder coating can further improve the powder coating edge coverage during spraying. Compared with Comparative Example 9 without the addition of such substances, although the synthesized acid value and viscosity index met the requirements, the powder coating at the edges and corners was inevitably slightly poor during the spraying process.

[0308] The above embodiments and comparative examples are for comparative reference only and are not intended to limit the implementation. Those skilled in the art can make other different combinations and variations based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any obvious variations or modifications arising therefrom are within the scope of protection of this invention.

Claims

1. A polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts, characterized in that, The polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts comprises the following raw materials in parts by weight: Neopentyl glycol 15-18 parts 20-25 parts terephthalic acid 2-4 parts adipic acid 0.3-0.5 parts of trimethylolpropane 10-13 parts of isophthalic acid 0.05 parts of esterification catalyst 0.5 parts antioxidant 0.2 parts of silane coupling agent 0.1 parts of charge adjuster 0.04 parts of curing accelerator; The charge modifier is SA2483 from Liuan Jietongda. The silane coupling agent is PTN101 from Suzhou Partner Environmental New Materials Co., Ltd.

2. The polyester resin for high-adhesion, high-edge-coverage powder coating of metal cutting parts according to claim 1, characterized in that, The polyester resin for high-adhesion, high-edge-coverage powder coating of metal cut parts comprises the following raw materials in parts by weight: 16 parts of neopentyl glycol 22 parts of terephthalic acid Adipic acid 2.7 parts 0.4 parts of trimethylolpropane 11 parts of isophthalic acid 0.05 parts of esterification catalyst 0.5 parts antioxidant 0.2 parts of silane coupling agent 0.1 parts of charge adjuster 0.04 parts of curing accelerator.

3. The polyester resin for high-adhesion, high-edge-coverage powder coating of metal-cut parts according to claim 1 or 2, characterized in that, The esterification catalyst is monobutyltin oxide.

4. The polyester resin for high-adhesion, high-edge-coverage powder coating of metal-cut parts according to claim 1 or 2, characterized in that, The antioxidants include BASF B900 compound antioxidants.

5. The polyester resin for high-adhesion, high-edge-coverage powder coating of metal-cut parts according to claim 1 or 2, characterized in that, The curing accelerator is benzyltriethylammonium chloride.

6. A method for preparing a polyester resin for a high-adhesion, high-edge-coverage powder coating for metal cutting parts as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: 1) Take the prescribed amounts of neopentyl glycol, trimethylolpropane, and terephthalic acid, mix them together, and add the prescribed amount of esterification catalyst into the reaction vessel. Heat to 200℃ and keep warm until the acid value is 5-10 mg KOH / g. 2) Add antioxidant and stir to mix well; 3) Add the prescribed amounts of adipic acid and isophthalic acid, heat to 240℃ and maintain the temperature, react until the acid value is 43-48 mgKOH / g, add the prescribed amounts of silane coupling agent and charge modifier, cool to 200℃ and apply vacuum until the acid value is 30-35 mgKOH / g, and the cone-plate viscosity of the resin is 3500-4000 mPa.s / 230℃; 4) Cool down to 185℃, add curing accelerator, stir evenly; after cooling, the product is ready.

7. The preparation method according to claim 6, characterized in that, The heat preservation mentioned in step 1) refers to heating to 200℃ and maintaining the temperature for 2 hours.

8. A powder coating, characterized in that, It is prepared using the polyester resin for high adhesion and high edge coverage powder coating of metal cutting parts as described in any one of claims 1-5.

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