CN111748082A - Special high-performance carboxyl-terminated polyester resin for powder coating and synthesis method thereof - Google Patents
Special high-performance carboxyl-terminated polyester resin for powder coating and synthesis method thereof Download PDFInfo
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- CN111748082A CN111748082A CN202010419752.7A CN202010419752A CN111748082A CN 111748082 A CN111748082 A CN 111748082A CN 202010419752 A CN202010419752 A CN 202010419752A CN 111748082 A CN111748082 A CN 111748082A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/66—Polyesters containing oxygen in the form of ether groups
- C08G63/668—Polyesters containing oxygen in the form of ether groups derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/672—Dicarboxylic acids and dihydroxy compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
- C09D167/06—Unsaturated polyesters having carbon-to-carbon unsaturation
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/03—Powdery paints
- C09D5/033—Powdery paints characterised by the additives
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2150/00—Compositions for coatings
- C08G2150/20—Compositions for powder coatings
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
- C08K2003/2237—Oxides; Hydroxides of metals of titanium
- C08K2003/2241—Titanium dioxide
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/30—Sulfur-, selenium- or tellurium-containing compounds
- C08K2003/3045—Sulfates
Abstract
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.
Description
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.
Example (b): 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:
the polyhydric alcohols include 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; the components are in any weight proportion; the weight portions of the polyhydric alcohol are as follows: 28 to 40
The polybasic acid comprises terephthalic acid, adipic acid, 1, 4-cyclohexane dicarboxylic acid, and isophthalic acid; the components are in any weight proportion; the polybasic acid comprises the following components in parts by weight: 41 to 49
Catalyst monobutyl tin oxide: 0.02 to 0.1
Antioxidant triphenyl phosphite: 0.2 to 0.8
Curing accelerator triphenyl phosphine ethyl bromide: 0.02 to 0.45;
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 adopting 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, opening an electric heating sleeve, starting stirring, regulating the speed to 20rpm, keeping the temperature to 80 ℃ until the materials are completely melted, adding terephthalic acid, adipic acid, 1, 4-cyclohexanedicarboxylic acid, isophthalic acid and monobutyltin oxide serving as a catalyst into the three-neck flask, starting stirring, regulating the speed to 20rpm, heating to 160 ℃, regulating the stirring speed to 70rpm, regulating the heating speed of the electric heating sleeve, heating to 240-neck flask according to the process requirement, maintaining the container until the materials are transparent, lowering the top temperature, and sampling to determine the acid value to be 5-30 mgKOH/g.
S2: when the temperature of the materials in the reaction vessel is reduced to 200-220 ℃, materials such as antioxidant triphenyl phosphite, isophthalic acid, trimellitic anhydride and the like are added, stirring is started, the stirring speed is adjusted to 70rpm, meanwhile, the heating speed of the electric heating sleeve is adjusted, the heating temperature is increased to 240-250 ℃, the top temperature is maintained to be reduced, and when the materials are colorless and transparent, sampling is carried out to detect that the acid value is 30-70 mgKOH/g.
S3: cooling the material to 240 ℃ for 210 plus materials, adjusting the stirring speed to 60rpm, starting a vacuum pump, slowly reducing the pressure and vacuum until the vacuum degree is-0.10 mPa, keeping the vacuum time at 30-90 minutes, sampling and detecting the acid value at 19-50mgKOH/g after stopping vacuum, then cooling the material to 220 ℃ for 190 plus materials, adding an antioxidant and a curing accelerator, uniformly stirring and discharging.
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.
The performance of the polyester resin is tested by index detection and test of the synthesized polyester resin and the powder coating and the coating prepared by taking the synthesized polyester resin as a base material; the test method comprises the following steps:
1. acid value:
the measurement was carried out according to the method of Standard GB/T6743-2008 "measurement of partial acid value and total acid value of Binder for polyester resin color paints and varnishes for plastics".
2. Melt viscosity:
the viscosity is determined according to the standard GB/T9751.1-2008 "color paints and varnishes part 1 with a rotary viscometer: the measurement was carried out by the method of Cone plate viscometer "operating at a high shear rate.
3. Softening point:
the determination was carried out according to the method of Standard GB/T12007.6-1989 method of epoxy resin softening Point determination by Ring and ball method.
4. Glass transition temperature:
according to standard GB/T19466.2-2004, section 2 of Differential Scanning Calorimetry (DSC) of plastics: measurement of glass transition temperature "was carried out by the method described in (1).
5. Impact properties:
the determination is carried out according to the method of the standard GB/T1732-1993 [ determination of the impact resistance of paint films ].
6. Gloss:
the determination is carried out according to the method of Standard GB/T9754-2007 determination of 20 °, 60 ° and 85 ° specular gloss of pigmented paint films, the pigmented paint and the clear paint not containing metallic pigments.
7. Hardness:
according to standard ISO 15184: 1998 determination of the hardness of the paint film by the colored paint and varnish-pencil method.
8. Adhesion force:
the determination is carried out according to the method of Standard GB/T9286-1998 test for marking test of paint and varnish films
9. Gel time:
measured according to the method of standard GB/T1699-1997 determination of the gelation time of thermosetting powder coatings at a given temperature.
TABLE 1 index for outdoor and indoor polyester and powder
Effect of polyol on low temperature curing of the polyester resin: the polyol monomer used for the polyester resin is based on economically viable neopentyl glycol and we have introduced various polyol monomers in this application to investigate their performance in low temperature curing of powder coatings. Take outdoor pure polyester type as an example.
TABLE 2 preparation of polyester resins from different polyols
TABLE 3 Effect of different types of polyols on powder coatings
Baking conditions: at 140 deg.C for 15 min
The polyester resins prepared after substituting neopentyl glycol with various glycols in an amount of 30% of the material exhibited the properties in the corresponding powder coatings, and the results are shown in tables 2 and 3. Three alcohols, ethylene glycol, diethylene glycol and 2-methyl-1, 3-propanediol, were found to exhibit poor storage stability and poor outdoor weatherability. The 2-butyl-2-ethyl-1, 3-propylene glycol shows higher gloss and appearance on the appearance of a powder coating, the powder coating corresponding to 1, 4-cyclohexanedimethanol is longer in gel time and reduced in performance, the coating corresponding to 1, 6-hexanediol is excellent in appearance and impact performance, the gel time is shortened, and the defects in beauty are that the prepared polyester resin is lower in glass transition temperature and poor in storage stability, 2-butyl-2-ethyl-1, 3-propylene glycol is introduced through optimization, a certain amount of 1, 6-hexanediol is introduced, an ideal polyester resin sample S-PR-8 is obtained, and the curing condition is that the polyester resin sample S-PR-8 is baked for 15 minutes at 180 ℃, so that the performance is better.
Effect of polybasic acid on low temperature curing of the polyester resin: the following polyacid monomers were compared for performance in place of terephthalic acid, and the results are shown in tables 4 and 5:
TABLE 4 preparation of polyester resins from different kinds of polybasic acids
TABLE 5 Effect of different types of polybasic acids on powder coatings
Description of the drawings: baking conditions: at 140 deg.C for 15 min
Adipic acid monomer exhibits better appearance and impact properties on powder coatings by comparing adipic acid, isophthalic acid and 1, 4-cyclohexanedicarboxylic acid in place of terephthalic acid in an amount of 25% of the material, because adipic acid has a flexible long chain structure, but after being made into a resin, the glass transition temperature was measured to be 55.9 ℃, and such a low temperature affects the storage stability of the resin and powder coating. After using isophthalic acid instead of terephthalic acid, the glass transition temperature of the prepared polyester resin is reduced and becomes more brittle, and although the prepared powder coating has a large change in gel time, from 107 seconds to 96 seconds, the recoiling performance of the coating is deteriorated. 1, 4-cyclohexanedicarboxylic acid is excellent in overall performance, the glass transition temperature is increased from 61.8 ℃ to 65.6 ℃, and the appearance, impact resistance and gloss of the coating of the powder coating are satisfactory. By combining the performances of several polybasic acid monomers, the monomer proportion of several polybasic acids is optimized to obtain the polyester resin sample S-PR-12 with excellent combination property. 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.
Effect of curing agent on the properties of the polyester resin: the curing accelerator is SA242 of Jietongda chemical engineering Limited liability company in Liuan, and the curing accelerator comprises triphenyl ethyl phosphine bromide with the molecular weight of 371.25, the melting point of 203-; the powder coatings and coatings were examined for their performance by adjusting the amount of triphenyl ethyl phosphine bromide used, and the results are shown in tables 6 and 7.
TABLE 6 preparation of polyester resins from Triphenylethylphosphine bromide
TABLE 7 Effect of Triphenylethylphosphine bromide on powder coating Properties
Description of the drawings: baking conditions: at 140 deg.C for 15 min
The influence of triphenyl ethyl phosphine bromide on the performance of the powder coating and the powder coating is very obvious, the curing temperature of the polyester resin and TGIC is greatly reduced after the addition, and the larger the addition is, the more the reduction is. Under the baking condition of 140 ℃ for 15 minutes, the addition amount of triphenyl ethyl phosphine bromide in the polyester resin sample S-PR-22 is moderate, and the addition amount of 2.1g ensures that the prepared powder coating can obtain 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.
The polyester resin and its synthesis are summarized by the above examples:
(1) the polyester resin is synthesized by a three-step synthesis method, 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 phosphine bromide and a composite antioxidant are added in the final synthesis stage.
(2) The acid value indoor type of the synthesized polyester resin is 70.7mgKOH/g, the melt viscosity is 3500mPa.s, and the softening point: 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 resin had 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 ℃ as analyzed by a differential scanning calorimeter.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
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.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114133538A (en) * | 2021-12-13 | 2022-03-04 | 安徽美佳新材料股份有限公司 | Special polyester resin for anti-sticking hanger powder coating and preparation method thereof |
| CN114350234A (en) * | 2021-12-27 | 2022-04-15 | 广东西敦千江粉漆科学研究有限公司 | High-toughness bending-resistant powder coating and preparation method thereof |
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| CN1282358A (en) * | 1997-12-18 | 2001-01-31 | Ucb公司 | Powder thermosetting compositions for preparing coatings with low gloss finish |
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| CN114350234A (en) * | 2021-12-27 | 2022-04-15 | 广东西敦千江粉漆科学研究有限公司 | High-toughness bending-resistant powder coating and preparation method thereof |
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Application publication date: 20201009 |