A 50 / 50 hybrid polyester resin for powder coating and its preparation method

Abstract

This invention relates to a polyester resin for 50 / 50 blended powder coatings. This polyester resin is obtained by reacting raw materials including glycerin black lead, ethylene glycol, diethylene glycol, terephthalic acid, 4,4'-biphenyl dicarboxylic acid, succinic acid, and pyromellitic dianhydride. The resulting product exhibits good impact resistance, a gloss level generally above 92%, and other properties such as adhesion that basically meet the application requirements of 50 / 50 blended powder coatings. Due to the comprehensive utilization of the effective components of glycerin black lead, it has the advantages of low cost and outstanding environmental performance.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, specifically to a 50 / 50 blended polyester resin for powder coating and its preparation method. Background Technology

[0002] Powder coatings are solid powdered synthetic resin coatings composed of solid resins, pigments, fillers, and additives. Unlike ordinary solvent-based and water-based coatings, their dispersion medium is air, not solvents or water. They feature solvent-free production, 100% film formation, and low energy consumption. Currently, powder coatings are widely used in indoor and outdoor coating applications as an environmentally friendly coating. Among them, indoor 50 / 50 mixed powder coatings are the most widely used due to their good overall performance. With the expansion of application areas, such as indoor metal surface coatings for ovens and pipes, the usage is significant, and reducing formulation costs is an important research direction for manufacturers. Glycerin black residue, a byproduct of stearic acid production, is formed when some glycerol polymerizes during high-temperature distillation of glycerol. The degree of polymerization is typically 2-4, resulting in a high viscosity of the remaining material. This makes it difficult to distill off the remaining glycerol, which eventually appears as a semi-solid residue known as glycerin black residue. Its main components are 15-20% glycerol, 14-18% polyglycerol, and the remainder being inorganic salts. It appears as a brown paste and is currently mostly disposed of by incineration, which not only wastes the organic matter such as glycerol and polyglycerol but also pollutes the environment.

[0003] To address the aforementioned problems, this invention utilizes raw materials including glycerol black residue, ethylene glycol, diethylene glycol, terephthalic acid, 4,4'-biphenyl dicarboxylic acid, succinic acid, and pyromellitic dianhydride. During the reaction, glycerol black residue is first dissolved with ethylene glycol and diethylene glycol. Then, activated clay and diatomaceous earth are added for decolorization and as filter aids. The mixture is then pressure filtered at a high temperature of 90-100℃ to obtain filtrate and inorganic particles. The filtrate is directly pumped into a reaction vessel and polymerized with terephthalic acid, 4,4'-biphenyl dicarboxylic acid, and succinic acid. Finally, high-functionality pyromellitic dianhydride is used for chain extension and end-capping treatment to obtain the final product. The resulting product exhibits good impact resistance, a gloss level generally above 92%, and other properties such as adhesion that basically meet the application requirements of 50 / 50 mixed powder coatings. Due to the comprehensive utilization of the effective components of glycerol black residue, it has the advantages of low cost and outstanding environmental performance. Summary of the Invention

[0004] This invention relates to a 50 / 50 hybrid polyester resin for powder coatings, which is prepared from raw materials including glycerin black lead, ethylene glycol, diethylene glycol, terephthalic acid, 4,4'-biphenyl dianhydride, succinic acid, pyromellitic dianhydride, activated clay, and diatomaceous earth. Specifically, it includes the following raw materials in parts by weight:

[0005]

[0006] The raw materials also include catalysts and antioxidants.

[0007] The glycerol black residue is a brown paste containing 15-20 wt% glycerol, 14-18 wt% polyglycerol, and the remainder being inorganic salts; it is commercially available, for example, from Rugao Shuangma Chemical Co., Ltd.

[0008] The catalyst is monobutyltin oxide, and its dosage is 0.05-0.1% of the total mass of the raw materials.

[0009] The antioxidant is antioxidant 1010, namely pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and its dosage is 0.05-0.1% of the total mass of the raw materials.

[0010] The preparation method of a 50 / 50 hybrid powder coating polyester resin as described above includes the following steps:

[0011] A. Add the prescribed amounts of ethylene glycol and diethylene glycol to the reaction vessel and stir until homogeneous, then heat to 90-100℃;

[0012] B. Add the prescribed amount of glycerol black residue to the reaction vessel, and fully dissolve and disperse it with the solution of ethylene glycol and diethylene glycol, while maintaining the temperature at 90-100℃;

[0013] C. When there are no obvious black glycerol particles in the reactor, add the formulated amount of activated clay and diatomaceous earth, stir for 0.5-1h, then reduce the stirring speed to 10-12 rpm, and filter the material under high temperature to obtain the filtrate.

[0014] D. The filtrate is pumped into the synthesis reactor and heated to 120-130℃. Then, the prescribed amounts of terephthalic acid and 4,4'-biphenyl dicarboxylic acid are added. After stirring and mixing evenly, the temperature is gradually increased to 200-205℃ and the reaction is carried out at this temperature.

[0015] E. Take samples for testing. When the acid value drops to below 30 mg KOH / g, add the amount of succinic acid specified in the formula, and then gradually raise the temperature to 225-230℃ and maintain the temperature for the reaction.

[0016] F. When the acid value of the polymer reaches 30-37 mg KOH / g, add a portion of the formulated amount of pyromellitic dianhydride and continue the chain extension reaction at 225-230℃.

[0017] G. When the acid value of the polymer reaches 25-33 mgKOH / g, add the prescribed amount of antioxidant, and then start the vacuum system to carry out vacuum polycondensation, maintaining the temperature at 225-230℃.

[0018] H. When the acid value of the polymer reaches 8-14 mgKOH / g, stop the vacuum system, add the remaining amount of pyromellitic dianhydride to carry out the end-capping reaction, and heat to 230-235℃ for heat preservation reaction. When the acid value of the polymer reaches 67-75 mgKOH / g, stop the reaction, discharge the material while it is hot, cool the polyester resin, and then crush and granulate it to obtain the final product.

[0019] In step C, the filter is filtered while hot using a plate and frame filter press. The pressure of the filter press is controlled at 1.2-1.5 MPa, and the filter cloth pore size is 300-350 mesh, resulting in a transparent filtrate and a brown filter cake. The filtrate is used for further reaction of the raw materials, and the filter cake is used as a de-icing agent.

[0020] In step D, the temperature is gradually increased to 200-205℃ at a heating rate of 9-12℃ / h; in step E, the temperature is gradually increased to 225-230℃ at a heating rate of 5-7℃ / h.

[0021] In step G, the vacuum level of the vacuum system is controlled between -0.096 MPa and -0.098 MPa; in step H, the polyester resin is cooled with a steel belt containing condensate.

[0022] In step F, one-third of the formula amount of pyromellitic dianhydride is added; in step H, the remaining formula amount of pyromellitic dianhydride is added.

[0023] For example, the preparation method of the polyester resin for the 50 / 50 hybrid powder coating includes the following steps:

[0024] A. Add the prescribed amounts of ethylene glycol and diethylene glycol to the reaction vessel and stir until homogeneous, then heat to 90-100℃;

[0025] B. Add the prescribed amount of glycerol black residue to the reaction vessel and fully dissolve and disperse it with the solution of ethylene glycol and diethylene glycol. Maintain the temperature at 90-100℃ to promote its dissolution and dispersion.

[0026] C. When there are no obvious glycerol black residue particles in the reaction vessel (particles smaller than 0.5 mm), it indicates that the effective components of the glycerol black residue, glycerol and polyglycerol, have been basically dispersed and dissolved in the hot solution of ethylene glycol and diethylene glycol. At this point, add the prescribed amount of activated clay and diatomaceous earth, stir for 0.5-1 hour, then reduce the stirring speed (e.g., to 10-12 rpm), and use a plate and frame filter press to filter the material while it is still hot. The pressure of the filter press is controlled at 1.2-1.5 MPa, and the filter cloth pore size is 300-350 mesh. A transparent filtrate and a brown filter cake are obtained respectively. The filtrate is used for further reaction of the raw materials, and the filter cake is used as a de-icing agent.

[0027] D. The filtrate is pumped into the synthesis reactor and heated to 120-130℃. Then, the prescribed amounts of terephthalic acid and 4,4'-biphenyl dicarboxylic acid are added. After stirring and mixing evenly, the temperature is gradually increased to 200-205℃ at a rate of 9-12℃ / h, and the reaction is carried out at this temperature.

[0028] E. Sampling and testing: When the acid value drops to below 30 mg KOH / g, add the amount of succinic acid specified in the formula, and then raise the temperature to 225-230℃ at a rate of 5-7℃ / h and maintain the temperature for reaction.

[0029] F. When the acid value of the polymer reaches 30-37 mg KOH / g, add one-third of the amount of pyromellitic dianhydride and continue the chain extension reaction at 225-230℃.

[0030] G. When the acid value of the polymer reaches 25-33 mgKOH / g, add the prescribed amount of antioxidant, then start the vacuum system, control the vacuum degree at -0.096Mpa to -0.098Mpa for vacuum polycondensation, and maintain the temperature at 225-230℃.

[0031] H. When the acid value of the polymer reaches 8-14 mgKOH / g, stop the vacuum system, add the remaining amount of pyromellitic dianhydride to carry out the end-capping reaction, and heat to 230-235℃ for heat preservation reaction. When the acid value of the polymer reaches 67-75 mgKOH / g, stop the reaction, discharge the material while it is hot, and cool the polyester resin with a steel belt with condensate, then crush and granulate to obtain the product.

[0032] The final product is a light yellow transparent granule with an acid value of 67-75 mgKOH / g and a softening point of 109-120℃.

[0033] The present invention also relates to the use of the polyester resin for 50 / 50 mixed powder coatings as described above or the polyester resin for 50 / 50 mixed powder coatings obtained by the preparation method described above in 50 / 50 powder coatings.

[0034] For example, a 50 / 50 mixed powder coating formulation includes: polyester resin, E-12 epoxy resin, titanium dioxide, barium sulfate, leveling agent, brightening agent, benzoin, etc.; the coating preparation method is as follows: mix the materials according to the powder coating formulation, extrude, press, and crush them separately using a twin-screw extruder, and then pulverize and sieve the sheets to make powder coating; the powder coating is sprayed onto a surface-treated tinplate substrate using an electrostatic spray gun and cured at 180℃ for 15 minutes to obtain the coating.

[0035] Beneficial effects:

[0036] The 50 / 50 hybrid powder coating polyester resin of this invention is prepared from raw materials including glycerol black lead, ethylene glycol, diethylene glycol, terephthalic acid, 4,4'-biphenyl dicarboxylic acid, succinic acid, pyromellitic dianhydride, activated clay, and diatomaceous earth. In the preparation method, glycerol black lead is first dissolved with ethylene glycol and diethylene glycol, then activated clay and diatomaceous earth are added for decolorization and as filter aids. The mixture is then pressure filtered at a high temperature of 90-100°C to obtain filtrate and inorganic particles. The filtrate is directly pumped into a reactor and polymerized with terephthalic acid, 4,4'-biphenyl dicarboxylic acid, and succinic acid. Finally, chain extension and end-capping treatment are performed using high-functionality pyromellitic dianhydride to obtain the final product. The resulting coating has good impact resistance, gloss is generally above 92%, and other properties such as adhesion basically meet the application requirements of 50 / 50 mixed powder coatings. Due to the comprehensive utilization of the effective components of glycerin black foot, it has the advantages of low cost and outstanding environmental performance. Detailed Implementation

[0037] The present invention will be further described below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0038] All raw materials used in this invention are commercially available. For example, glycerol black residue is a brown paste containing 15-20 wt% glycerol, 14-18 wt% polyglycerol, and the remainder being inorganic salts; it was purchased from Rugao Shuangma Chemical Co., Ltd.

[0039] Preparation Example 1

[0040] A 50 / 50 blended polyester resin for powder coatings comprises the following raw materials in parts by weight:

[0041]

[0042]

[0043] The catalyst is monobutyltin oxide, and its dosage is 0.1% of the total mass of the raw materials; the antioxidant is antioxidant 1010, and its dosage is 0.1% of the total mass of the raw materials.

[0044] The preparation method of the polyester resin for the 50 / 50 hybrid powder coating includes the following steps:

[0045] A. Add the prescribed amounts of ethylene glycol and diethylene glycol to the reaction vessel and stir until homogeneous, then heat to 90°C;

[0046] B. Add the prescribed amount of glycerol black residue to the reaction vessel and fully dissolve and disperse it with the solution of ethylene glycol and diethylene glycol. Maintain the temperature at 90℃ to promote its dissolution and dispersion.

[0047] C. When there are no obvious glycerol black residue particles in the reaction vessel (particles smaller than 0.5 mm), it indicates that the effective components of the glycerol black residue, glycerol and polyglycerol, have been basically dispersed and dissolved in the hot solution of ethylene glycol and diethylene glycol. At this point, add the prescribed amount of activated clay and diatomaceous earth, stir for 1 hour, then reduce the stirring speed to 10-12 rpm, and use a plate and frame filter press to filter the material while it is still hot. The pressure of the filter press is controlled at 1.2 MPa, and the filter cloth pore size is 300 mesh. A transparent filtrate and a brown filter cake are obtained respectively. The filtrate is used for further reaction of the raw materials, and the filter cake is used as a de-icing agent.

[0048] D. The filtrate is pumped into the synthesis reactor and heated to 120°C. Then, the prescribed amounts of terephthalic acid and 4,4'-biphenyl dicarboxylic acid are added. After stirring and mixing evenly, the temperature is gradually increased to 200°C at a rate of 9°C / h, and the reaction is carried out under heat.

[0049] E. Sampling and testing: When the acid value drops to below 30 mg KOH / g, add the prescribed amount of succinic acid, and then heat to 225°C at a rate of 5°C / h and maintain the temperature for reaction.

[0050] F. When the acid value of the polymer reaches 30-37 mg KOH / g, add one-third of the amount of pyromellitic dianhydride and continue the chain extension reaction at 225℃.

[0051] G. When the acid value of the polymer reaches 25-33 mgKOH / g, add the prescribed amount of antioxidant, then start the vacuum system, control the vacuum degree at -0.096 MPa for vacuum polycondensation, and maintain the temperature at 225℃.

[0052] H. When the acid value of the polymer reaches 8-14 mgKOH / g, stop the vacuum system, add the remaining amount of pyromellitic dianhydride to carry out the end-capping reaction, and heat to 230-235℃ for heat preservation reaction. When the acid value of the polymer reaches 67-75 mgKOH / g, stop the reaction, discharge the material while it is hot, and cool the polyester resin with a steel belt with condensate, then crush and granulate to obtain the product.

[0053] The resulting product is a light yellow transparent granule with an acid value of 69 mg KOH / g and a softening point of 113℃.

[0054] Preparation Example 2

[0055] A 50 / 50 blended polyester resin for powder coatings comprises the following raw materials in parts by weight:

[0056]

[0057] The catalyst is monobutyltin oxide, and its dosage is 0.1% of the total mass of the raw materials.

[0058] The antioxidant is antioxidant 1010, namely pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and its dosage is 0.1% of the total mass of the raw materials.

[0059] The preparation method is the same as in Preparation Example 1.

[0060] The resulting product is a light yellow transparent granule with an acid value of 74 mg KOH / g and a softening point of 118℃.

[0061] Preparation Example 3

[0062] A 50 / 50 blended polyester resin for powder coatings comprises the following raw materials in parts by weight:

[0063]

[0064] The catalyst is monobutyltin oxide, and its dosage is 0.05% of the total mass of the raw materials.

[0065] The antioxidant is antioxidant 1010, namely pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and its dosage is 0.05% of the total mass of the raw materials.

[0066] The preparation method is the same as in Preparation Example 1.

[0067] The resulting product is a light yellow transparent granule with an acid value of 71 mg KOH / g and a softening point of 112℃.

[0068] Preparation Example 4

[0069] A 50 / 50 blended polyester resin for powder coatings comprises the following raw materials in parts by weight:

[0070]

[0071]

[0072] The catalyst is monobutyltin oxide, and its dosage is 0.1% of the total mass of the raw materials.

[0073] The antioxidant is antioxidant 1010, namely pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and its dosage is 0.05% of the total mass of the raw materials.

[0074] The preparation method is the same as in Preparation Example 1.

[0075] The resulting product is a light yellow transparent granule with an acid value of 71 mg KOH / g and a softening point of 114℃.

[0076] Comparative preparation example 1:

[0077] Commercially available general-purpose 50 / 50 polyester resin, acid value 72mgKOH / g, softening point 116℃, model ZJ5050, Huangshan Zhengjie New Materials Co., Ltd.

[0078] Examples 1-4, Comparative Example 1 (polyester resins were obtained from Preparation Examples 1-4 and Comparative Preparation Example 1, respectively):

[0079] The general-purpose 50 / 50 mixed powder coating formulation, by weight, is as follows:

[0080]

[0081] Coating preparation: Mix all materials according to the above powder coating formula, extrude, press, and crush using a twin-screw extruder, then pulverize and sieve the sheet (150-180 mesh) to produce powder coating. Apply the powder coating to a surface-treated tinplate substrate using an electrostatic spray gun, achieving a film thickness of approximately 80 μm. Curing is then performed at 180℃ for 15 minutes to obtain the coating layer.

[0082] Performance Comparison

[0083] Coating index testing is based on GB / T 21776-2008 "Guidelines for Testing Powder Coatings and Their Coatings".

[0084] The results of testing the coating performance of the polyester resins prepared according to the coating formulations provided by the present invention are shown in Table 1 below.

[0085] Table 1 Performance of Powder Coating Film

[0086] sample Coating appearance Impact resistance (50cm) Gloss (60° angle) Adhesion Boil in boiling water for 2 hours. Example 1 Smooth Both positive and negative impacts passed 93.4％ 0 No change Example 2 Smooth Both positive and negative impacts passed 93.7％ 0 No significant changes Example 3 Smooth Both positive and negative impacts passed 93.5％ 0 No change Example 4 Smooth Both positive and negative impacts passed 93.1％ 0 No change Comparative Example 1 Smooth Both positive and negative impacts passed 93.8％ 0 No change

[0087] As can be seen from the table above, the coating film prepared by the product of this invention has a smooth and even appearance, passes the 50cm forward and reverse impact smoothly, has a gloss level of over 93%, achieves an adhesion grade of 0, and shows no significant change after boiling in water for 2 hours. Its overall performance is excellent, and there is no significant difference compared to commercially available 50 / 50 polyester resin products (Comparative Example 1). This invention not only reduces formulation costs and yields a low-cost 50 / 50 polyester resin product, but also develops a new approach for the high-value comprehensive utilization of glycerin black residue, possessing significant environmental and economic benefits.

[0088] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above description is illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A polyester resin for 50 / 50 blended powder coatings, characterized in that, Includes the following raw materials in parts by weight: Glycerin for black feet (8-10 parts); 15-18 parts of ethylene glycol; Diethylene glycol 3-5 parts; 22-27 parts of terephthalic acid; 1-2 parts of 4,4'-biphenyl dicarboxylic acid; 12-15 parts of succinic acid; 5-7 parts of pyromellitic dianhydride; 0.08-0.12 parts of activated clay; Diatomaceous earth 0.02-0.05 parts; The raw materials also include catalysts and antioxidants; The glycerol black residue is a brown paste containing 15-20 wt% glycerol, 14-18 wt% polyglycerol, and the remainder being inorganic salts; the catalyst is monobutyltin oxide, used at 0.05-0.1% of the total raw material mass; the antioxidant is antioxidant 1010, used at 0.05-0.1% of the raw material mass. The preparation method includes the following steps: A. Add the prescribed amounts of ethylene glycol and diethylene glycol to the reaction vessel and stir until homogeneous, then heat to 90-100℃; B. Add the prescribed amount of glycerol black residue to the reaction vessel, and fully dissolve and disperse it with the solution of ethylene glycol and diethylene glycol, while maintaining the temperature at 90-100℃; C. When there are no obvious black glycerol particles in the reactor, add the formulated amount of activated clay and diatomaceous earth, stir for 0.5-1 hour, then reduce the stirring speed and filter the mixture at high temperature to obtain the filtrate. D. The filtrate is pumped into the synthesis reactor and heated to 120-130℃. Then, the prescribed amounts of terephthalic acid and 4,4'-biphenyl dicarboxylic acid are added. After stirring and mixing evenly, the temperature is gradually increased to 200-205℃ and the reaction is carried out at this temperature. E. Take samples for testing. When the acid value drops to below 30 mg KOH / g, add the amount of succinic acid specified in the formula, and then gradually raise the temperature to 225-230℃ and maintain the temperature for the reaction. F. When the acid value of the polymer reaches 30-37 mg KOH / g, add a portion of the formulated amount of pyromellitic dianhydride and continue the chain extension reaction at 225-230℃. G. When the acid value of the polymer reaches 25-33 mgKOH / g, add the prescribed amount of antioxidant 1010, and then start the vacuum system to carry out vacuum polycondensation, maintaining the temperature at 225-230℃. H. When the acid value of the polymer reaches 8-14 mgKOH / g, stop the vacuum system, add the remaining amount of pyromellitic dianhydride to carry out the end-capping reaction, and heat to 230-235℃ for heat preservation reaction. When the acid value of the polymer reaches 67-75 mgKOH / g, stop the reaction, discharge the material while it is hot, cool the polyester resin, and then crush and granulate it to obtain the final product.

2. The polyester resin for 50 / 50 mixed powder coating as described in claim 1, further characterized in that, in step C of the preparation method, the material is discharged by hot high-temperature pressure filtration using a plate and frame filter press, the pressure of the filter press is controlled at 1.2-1.5 MPa, the pore size of the filter cloth is 300-350 mesh, and transparent filtrate and brown filter cake are obtained respectively; the filtrate is used for further reaction of raw materials, and the filter cake is used as a de-icing agent.

3. The polyester resin for 50 / 50 mixed powder coating as described in claim 1, further characterized in that, in step D of the preparation method, the temperature is gradually increased to 200-205℃ at a heating rate of 9-12℃ / h; and in step E, the temperature is gradually increased to 225-230℃ at a heating rate of 5-7℃ / h.

4. The polyester resin for 50 / 50 mixed powder coating as described in claim 1, further characterized in that, in step G of the preparation method, the vacuum degree of the vacuum system is controlled at -0.096 MPa to -0.098 MPa; in step H, the polyester resin is cooled with a steel belt containing condensate.

5. The polyester resin for 50 / 50 mixed powder coating as described in claim 1, further characterized in that, in step F of the preparation method, one-third of the formulation amount of pyromellitic dianhydride is added; and in step H, the remaining formulation amount of pyromellitic dianhydride is added.

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