阅读说明：本技术 一种粉末涂料专用高性能端羧基聚酯树脂及其合成方法 (Special high-performance carboxyl-terminated polyester resin for powder coating and synthesis method thereof ) 是由 王方银 于 2020-05-18 设计创作，主要内容包括：本发明公开了一种粉末涂料专用高性能端羧基聚酯树脂及其合成方法,本发明解决现有以TGIC作为固化剂制备的户外粉末涂料,固化条件都在200℃×10分钟以上,以环氧树脂作为固化剂的户内粉末涂料固化条件在180℃×10分钟,固化温度过高,造成能源的大量浪费,烘烤时间长,使得生产的周期长,增加了设备和人力的成本问题,通过对制备粉末涂料用的聚酯树脂单体进行改良和优化,使得这种聚酯树脂稳定性好,能够在相对较低的温度下使得粉末涂料固化,且低温固化也使得粉末涂料能够扩大使用范围,同时也能提高加工效率,大幅度降低了生产成本,避免了通过传统聚酯树脂合成的粉末涂料容易造成大量能源浪费的问题。(The invention discloses a special high-performance carboxyl-terminated polyester resin for powder coating and a synthesis method thereof, which solves the problems that the curing conditions of the existing outdoor powder coating prepared by taking TGIC as a curing agent are more than 200 ℃ for 10 minutes, the curing condition of the indoor powder coating taking the epoxy resin as the curing agent is multiplied by 10 minutes at 180 ℃, the curing temperature is too high, a great deal of energy is wasted, the baking time is long, the production period is long, the cost of equipment and manpower is increased, by improving and optimizing the polyester resin monomer for preparing the powder coating, the polyester resin has good stability, can solidify the powder coating at relatively low temperature, can expand the application range of the powder coating by low-temperature solidification, meanwhile, the processing efficiency can be improved, the production cost is greatly reduced, and the problem that a large amount of energy is wasted easily caused by powder coating synthesized by the traditional polyester resin is solved.)

1. A high-performance carboxyl-terminated polyester resin special for powder coating, the acid value indoor type is 70.7mgKOH/g, the melt viscosity is 3500mPa.s, the softening point: 106 ℃, the number average molecular weight of the resin is 3209, the weight average molecular weight is 5425, the molecular weight distribution is 1.53, and the glass transition temperature of the resin is 53.52 ℃; the outdoor value of the acid value is 35.6mgKOH/g, the melt viscosity is 5500mPa.s, the softening point: 116 ℃, the resin has a number average molecular weight of 5506, a weight average molecular weight of 8356, a molecular weight distribution of 1.48, and a glass transition temperature of 63.46 ℃, and is obtained by melt polycondensation of the following raw materials in parts by weight:

polyol: 28 to 40

Polybasic acid: 41 to 49

Catalyst: 0.02 to 0.1

Antioxidant: 0.2 to 0.8

Curing accelerator: 0.02 to 0.45;

the polyhydric alcohols comprise neopentyl glycol and ethylene glycol, and also comprise 2-methyl-1, 3-propanediol, 1, 6-hexanediol, 1, 4-cyclohexanedimethanol, 2-butyl-2-ethyl-1, 3-propanediol, diethylene glycol and trimethylolpropane; the components are in any weight proportion;

the polybasic acid comprises terephthalic acid, adipic acid, 1, 4-cyclohexanedicarboxylic acid and isophthalic acid; the components are in any weight ratio.

2. The special high-performance carboxyl-terminated polyester resin for powder coating as claimed in claim 1, wherein the catalyst is monobutyl tin oxide.

3. The special high-performance carboxyl-terminated polyester resin for powder coating as claimed in claim 2, wherein the antioxidant is triphenyl phosphite.

4. The special high-performance carboxyl-terminated polyester resin for powder coatings and the synthesis method thereof as claimed in claim 3, are characterized in that the curing accelerator is triphenyl ethyl phosphine bromide.

5. The method for synthesizing the special high-performance carboxyl-terminated polyester resin for the powder coating as claimed in claim 1, wherein the method for synthesizing the high-performance carboxyl-terminated polyester resin is prepared by a three-step method, and comprises the following specific steps:

s1: adding neopentyl glycol, ethylene glycol, 2-methyl-1, 3-propanediol, 1, 6-hexanediol, 1, 4-cyclohexanedimethanol, 2-butyl-2-ethyl-1, 3-propanediol, diethylene glycol, trimethylolpropane and water into a 2000ml three-neck flask according to the formula amount, turning on an electric heating sleeve, starting stirring, adjusting the speed to 20rpm, raising the temperature to 80 ℃ and keeping the temperature until the materials are completely melted, then adding terephthalic acid, adipic acid, 1, 4-cyclohexanedicarboxylic acid, isophthalic acid and monobutyltin oxide serving as a catalyst into a three-neck flask, starting stirring, regulating the speed to 20rpm, heating to 160 ℃, regulating the stirring speed to 70rpm, meanwhile, the temperature rise speed of the electric heating jacket is adjusted, and the temperature rises to 240-250 ℃ according to the process requirement.

S2: when the temperature of the materials in the reaction vessel is reduced to 200-220 ℃, the materials such as antioxidant triphenyl phosphite, isophthalic acid, trimellitic anhydride and the like are added, the stirring is started, the stirring speed is adjusted to 70rpm, meanwhile, the heating speed of the electric heating jacket is adjusted, and the heating temperature is increased to 240-250 ℃.

S3: cooling the material to 210-240 ℃, adjusting the stirring speed to 60rpm, starting the vacuum pump, sampling and detecting the acid value to be 19-50mgKOH/g after stopping the vacuum pump, then cooling the material to 190-220 ℃, adding the antioxidant and the curing accelerator, uniformly stirring, and discharging.

6. The method as claimed in claim 5, wherein the temperature of step S1 is increased to 240-250 ℃ until the material in the container is transparent, the top temperature is decreased, and then the acid value is measured by sampling 5-30 mgKOH/g.

7. The method as claimed in claim 6, wherein in step S2, when the temperature is increased to 240-250 ℃ and the material is colorless and transparent, the sample is taken to detect the acid value at 30-70 mgKOH/g.

8. The method for synthesizing high-performance carboxyl-terminated polyester resin specially used for powder coating as claimed in claim 7, wherein after the vacuum pump is turned on in step S3, the vacuum is slowly reduced to a vacuum degree of-0.10 mPa for 30-90 minutes.

Technical Field

The invention relates to the technical field of powder coating, in particular to a special high-performance carboxyl-terminated polyester resin for powder coating and a synthesis method thereof.

Background

Thermosetting powder coating is widely applied at home and abroad due to the characteristics of no pollution, resource saving, high efficiency and the like, along with the increasing requirements of the market on the board surface of the powder coating and the performance of the coating, the performance requirements of the polyester resin which is the main raw material of the powder coating are also increasing, the polyester resin special for the powder coating belongs to saturated resin, the polyester resin can be mainly classified into hydroxyl-terminated polyester resin and carboxyl-terminated polyester resin according to the terminal functional group, the hydroxyl value of the hydroxyl-terminated polyester resin is between 30 and 300mgKOH/g, the caprolactam-sealed isocyanate is generally used as the curing agent of the powder coating, the excellent weather resistance and corrosion resistance can be realized, the prospect is extremely wide, and the powder coating taking the carboxyl-terminated polyester resin as the base material occupies larger proportion in the development in recent years. Generally, the carboxyl-terminated polyester resin has an acid value of 19 to 80mgKOH/g, and is classified into an epoxy resin-cured indoor mixed powder coating, a pure polyester powder coating using hydroxyalkylamide as a curing agent, and a pure polyester powder coating using TGIC as a curing agent by the category of the curing agent; however, the conventional polyester resin for powder coating has the following problems: the existing outdoor powder coating prepared by using TGIC as a curing agent has the curing condition of more than 200 ℃ multiplied by 10 minutes, the curing condition of the indoor powder coating using epoxy resin as the curing agent is 180 ℃ multiplied by 10 minutes, the curing temperature is too high, a great deal of energy waste is caused, the baking time is long, the production time period is long, and the equipment and labor cost is increased.

With the increasing requirements on energy conservation and emission reduction and the defect that powder coatings such as heat-sensitive substrates cannot be coated, the curing temperature is reduced, and the curing speed is increased, so that the novel expansion space of the industry is formed.

Disclosure of Invention

The invention aims to provide a high-performance carboxyl-terminated polyester resin special for a powder coating, which aims to solve the problems that the existing outdoor powder coating prepared by taking TGIC as a curing agent has the curing condition of more than 200 ℃ multiplied by 10 minutes, the indoor powder coating prepared by taking epoxy resin as the curing agent has the curing condition of 180 ℃ multiplied by 10 minutes, the curing temperature is too high, a large amount of energy is wasted, the baking time is long, the production time period is long, and the cost of equipment and manpower is increased.

The second purpose of the invention is to provide a method for synthesizing the high-performance carboxyl-terminated polyester resin special for the powder coating, so as to prepare the high-performance carboxyl-terminated polyester resin meeting the requirements.

The first purpose of the invention is realized by the following technical scheme:

a high-performance carboxyl-terminated polyester resin special for powder coating, the acid value indoor type is 70.7mgKOH/g, the melt viscosity is 3500mPa.s, the softening point: 106 ℃, the number average molecular weight of the resin is 3209, the weight average molecular weight is 5425, the molecular weight distribution is 1.53, the glass transition temperature of the resin is 53.52 ℃, the outdoor value of the acid value is 35.6mgKOH/g, the melt viscosity is 5500mPa.s, the softening point: 116 ℃, the resin has a number average molecular weight of 5506, a weight average molecular weight of 8356, a molecular weight distribution of 1.48, and a glass transition temperature of 63.46 ℃, and is obtained by melt polycondensation of the following raw materials in parts by weight:

polyol: 28 to 40

Polybasic acid: 41 to 49

Catalyst: 0.02 to 0.1

Antioxidant: 0.2 to 0.8

Curing accelerator: 0.02 to 0.45;

the polyhydric alcohols comprise neopentyl glycol and ethylene glycol, and also comprise 2-methyl-1, 3-propanediol, 1, 6-hexanediol, 1, 4-cyclohexanedimethanol, 2-butyl-2-ethyl-1, 3-propanediol, diethylene glycol and trimethylolpropane; the components are in any weight proportion;

the polybasic acid comprises terephthalic acid, adipic acid, 1, 4-cyclohexanedicarboxylic acid and isophthalic acid; the components are in any weight ratio.

Further, the catalyst is monobutyl tin oxide.

Further, the antioxidant is triphenyl phosphite.

Further, the curing accelerator is triphenyl ethyl phosphine bromide.

The second purpose of the invention is realized by the following technical scheme:

a synthetic method of high-performance carboxyl-terminated polyester resin special for powder coating is characterized in that the synthetic method of the high-performance carboxyl-terminated polyester resin is prepared by a three-step method, and comprises the following specific steps:

s1: adding neopentyl glycol, ethylene glycol, 2-methyl-1, 3-propanediol, 1, 6-hexanediol, 1, 4-cyclohexanedimethanol, 2-butyl-2-ethyl-1, 3-propanediol, diethylene glycol, trimethylolpropane and water into a 2000ml three-neck flask according to the formula amount, turning on an electric heating sleeve, starting stirring, adjusting the speed to 20rpm, raising the temperature to 80 ℃ and keeping the temperature until the materials are completely melted, then adding terephthalic acid, adipic acid, 1, 4-cyclohexanedicarboxylic acid, isophthalic acid and monobutyltin oxide serving as a catalyst into a three-neck flask, starting stirring, regulating the speed to 20rpm, heating to 160 ℃, regulating the stirring speed to 70rpm, meanwhile, the temperature rise speed of the electric heating jacket is adjusted, and the temperature rises to 240-250 ℃ according to the process requirement.

S2: when the temperature of the materials in the reaction vessel is reduced to 200-220 ℃, the materials such as antioxidant triphenyl phosphite, isophthalic acid, trimellitic anhydride and the like are added, the stirring is started, the stirring speed is adjusted to 70rpm, meanwhile, the heating speed of the electric heating jacket is adjusted, and the heating temperature is increased to 240-250 ℃.

S3: cooling the material to 210-240 ℃, adjusting the stirring speed to 60rpm, starting the vacuum pump, sampling and detecting the acid value to be 19-50mgKOH/g after stopping the vacuum pump, then cooling the material to 190-220 ℃, adding the antioxidant and the curing accelerator, uniformly stirring, and discharging.

Further, in the step S1, when the temperature is increased to 240 ℃ and 250 ℃ according to the process requirements, the material in the container is kept transparent, the top temperature is reduced, and then a sample is taken to determine that the acid value is 5-30 mgKOH/g.

Further, in the step S2, when the temperature is increased to 240-250 ℃ according to the process requirements and the top temperature is maintained to be reduced, and the material is colorless and transparent, the acid value is detected by sampling to be 30-70 mgKOH/g.

Further, in the step S3, after the vacuum pump is turned on, the vacuum is slowly reduced to the vacuum degree of-0.10 mPa, and the vacuum time is 30-90 minutes.

The method for preparing the powder coating by using the high-performance carboxyl-terminated polyester resin comprises the steps of proportioning the prepared polyester resin indoor type, epoxy resin and outdoor type with TGIC in proportion, using titanium dioxide as pigment, using precipitated barium sulfate as filler, matching with acrylic leveling agent, brightener and benzoin used as degasifier, fully and uniformly mixing, setting the front zone temperature of a double-screw extruder at 120 ℃, setting the rear zone temperature at 105 ℃, starting a screw, setting the rotating speed of the screw at 30rpm, putting the fully mixed powder premix into a hopper of the extruder, keeping constant-speed melting, mixing and extruding, carrying out double-roller tabletting, cooling, grinding by using a high-speed mill, and sieving. The tin plate is subjected to oil and rust removal treatment by using alcohol, then the sieved powder coating is sprayed on the tin plate by using an electrostatic spray gun, and then the tin plate is lightly put into a preheated electric heating box for baking for a proper time and then taken out for later use.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the invention, 2-butyl-2-ethyl-1, 3-propylene glycol is introduced into the polyhydric alcohol, and a certain amount of 1, 6-hexanediol is introduced, so that an ideal polyester resin sample S-PR-8 is obtained, the curing condition is 180 ℃ for 15 minutes, and the performance is better.

(2) The invention optimizes the monomer proportion of several polybasic acids to obtain the polyester resin sample S-PR-12 with excellent comprehensive performance. Although the gelling time is slightly shortened on the basis of S-PR-8, the weather resistance of the coating is greatly improved because more 1, 4-cyclohexanedicarboxylic acid and isophthalic acid are introduced during synthesis.

(3) According to the curing accelerator disclosed by the invention, triphenyl ethyl phosphonium bromide is adopted to have very obvious influence on the performance of the powder coating and the powder coating, the curing temperature of polyester resin and TGIC is greatly reduced after the curing accelerator is added, the larger the addition is, the more the reduction is, the addition amount of triphenyl ethyl phosphonium bromide in a polyester resin sample S-PR-22 is moderate under the baking condition of 140 ℃ multiplied by 15 minutes, and the addition amount of 2.1g ensures that the prepared powder coating can obtain the smooth and flat powder coating appearance and can also ensure the impact property of the coating. After the addition amount of the powder coating exceeds 2.1g, the gel time of the powder coating is short, when the powder coating is not completely melted and flowed, the coating is quickly cured under the action of triphenyl ethyl phosphine bromide, the orange peel of the coating is obvious, and the leveling is poor.

(4) The invention adopts a three-step synthesis method to synthesize the polyester resin, namely three stages of polycondensation, acidolysis and vacuum. Isophthalic acid, adipic acid, fumaric acid, 1, 4-cyclohexanedicarboxylic acid, 1, 6-hexanediol, 2-butyl-2-ethyl-1, 3-propanediol are introduced into polyester resin, a proper amount of trimethylolpropane is added to synthesize the polyester resin, the storage stability is good, and ethyl triphenyl phosphonium bromide and a composite antioxidant are added in the final synthesis stage.

(5) The acid value indoor type of the synthesized polyester resin is 70.7mgKOH/g, the melt viscosity is 3500mPa.s, the softening point is as follows: at 106 deg.c. After infrared spectroscopic analysis, the number average molecular weight of the resin is 3209, the weight average molecular weight is 5425, the molecular weight distribution is 1.53, the molecular weight distribution is normal distribution and narrow, which indicates that the molecular weight distribution is relatively uniform, and the glass transition temperature of the resin analyzed by a differential scanning calorimeter is 53.52 ℃; outdoor type of 35.6mgKOH/g, melt viscosity of 5500mPa.s, softening point: 116 ℃. The number average molecular weight of the resin is 5506, the weight average molecular weight is 8356, the molecular weight distribution is 1.48, the glass transition temperature of the resin analyzed by a differential scanning calorimeter is 63.46 ℃, the polyester resin with the structure can improve the processing efficiency, save energy, reduce consumption, greatly reduce the production cost and avoid the problem that the powder coating synthesized by the traditional polyester resin easily causes a large amount of energy waste.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.