CN113980253B - Bending-resistant easy-extinction polyester resin for low-curing-agent-consumption powder coating and preparation method thereof - Google Patents
Bending-resistant easy-extinction polyester resin for low-curing-agent-consumption powder coating and preparation method thereof Download PDFInfo
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- CN113980253B CN113980253B CN202111192436.1A CN202111192436A CN113980253B CN 113980253 B CN113980253 B CN 113980253B CN 202111192436 A CN202111192436 A CN 202111192436A CN 113980253 B CN113980253 B CN 113980253B
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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
- C08G63/64—Polyesters containing both carboxylic ester groups and carbonate groups
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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
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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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- 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
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- 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 polyester resin for a bending-resistant, extinction-prone and low-curing agent dosage powder coating and a preparation method thereof, wherein the acid value of the polyester resin is 19-29 mgKOH/g, the melt viscosity at 200 ℃ is 6000-9000 mPa.s, the glass transition temperature is 56-65 ℃, the reactivity at 180 ℃ is 350-550 s, and the polyester resin is mainly prepared by carrying out melt polycondensation on the following raw materials: polyol, polycarbonate diol, dibasic acid, acidolysis agent, capping agent, catalyst, curing accelerator and antioxidant. The extinction powder coating prepared from the polyester resin has excellent mechanical properties, meets the requirement of bending-resistant post-forming processing, and has excellent extinction performance and leveling performance.
Description
Technical Field
The invention belongs to the technical field of polyester resin, and particularly relates to a bending-resistant easy-extinction polyester resin for a low-curing agent dosage powder coating and a preparation method thereof.
Background
Depending on the gloss of the coating, powder coatings can be divided into high-gloss, semi-gloss and matte powder coatings. With the change of aesthetic level of people and the problem of light pollution caused by a high-gloss coating, the extinction powder coating with a soft surface decoration effect is more and more widely applied, and meanwhile, the extinction powder coating has the advantages of being capable of masking slight paint film defects and improving durability and the like and is more and more favored by people. In addition, because the surface shape of the formed material is different, certain difficulty exists in powder spraying, and the powder spraying is simpler before the base material is formed, the method that the base material is pre-coated with the powder coating firstly and then the powder coating is formed by punching and the like is adopted in the field of more complex sectional materials, so that the mode that manufacturers use the powder coating more and more commonly is adopted. The press forming is a processing and forming method for obtaining a workpiece (stamping part) with a required shape and size by applying external force to a base material by a press and a die to deform the base material, but the post-forming mode such as press forming and the like has higher requirements on the bending resistance of the powder coating due to the external force action. In domestic outdoor extinction powder coatings, the polyester/TGIC (triglycidyl isocyanurate) system is most widely applied, and two extinction modes are provided, namely extinction by adding an extinction agent and dry mixing extinction. The extinction of the extinction agent is realized by adding the extinction agent outside the single-component resin; dry-blending matting is achieved by the difference in reactivity of the respective components in a two-component or multi-component resin. However, the extinction coatings obtained by different methods have the problems of poor impact resistance and the like, are difficult to meet the use requirements of post-forming processing such as bending and deep drawing after pre-coating the base material, and seriously restrict the development of practical application.
TGIC is used as a common curing agent of thermosetting powder coating, and the powder coating prepared by the TGIC has excellent comprehensive performance, but the TGIC has higher price and certain toxicity, so powder coating manufacturers urgently need low curing agent (TGIC) powder coatings. The acid value of the polyester resin for powder coating determines the using amount of the curing agent, generally, the low acid value polyester needs to be matched with the TGIC using amount to be reduced, and the reduction of the acid value can cause the reduction of the activity of the powder coating and the reduction of the cross-linking density of the powder coating, thereby seriously influencing the application performance of the powder coating. In the extinction type powder coating, the extinction agent is added into the low acid value polyester for extinction, the extinction agent has a large negative effect on the mechanical property of a coating, and meanwhile, the mechanical property is reduced due to the low content of the curing agent matched with the low acid value, so that the bending resistance requirement required in the post-forming processing process cannot be met.
Chinese patent CN103739830B discloses a polyester resin for TGIC curing high-toughness powder coating and a preparation method thereof, a powder coating prepared from the polyester resin has excellent flexibility, has excellent mechanical properties at normal temperature and low temperature of about-10 ℃, but has higher acid value, belongs to a polyester/TGIC type 93/7 conventional product, and is used for preparing a high-gloss coating; chinese patent CN109054003B discloses a polyester resin for TGIC curing extinction powder coating and a preparation method thereof, compared with the existing TGIC system extinction powder coating, the powder coating prepared by adopting the polyester has better extinction effect, better shock resistance and powder coating storage stability, but the acid value of the polyester is higher, and the polyester belongs to a polyester/TGIC type 93/7 conventional product; chinese patent CN110964108a discloses a polyester resin for matting powder coating, a powder coating and a preparation method thereof, the powder coating prepared by using the polyester resin has good levelling property, good impact resistance and bending resistance, and can obtain 5 to 7% of low gloss under the condition of adding a matting agent, however, the acid value of the polyester resin expressed in the claims of the application is 5 to 10mgKOH/g, and the contents of polyester and a curing agent are close to 2:1, the product does not belong to a polyester/TGIC system, and the product performances are obviously different; chinese patent CN103214660A discloses a polyester resin for a two-component extinction type powder coating and a preparation method thereof, and the powder coating is prepared by respectively adopting A/B group polyester. The extinction coating with 5% -50% of gloss can be obtained by mixing according to different proportions, however, the application does not describe the indexes of polyester and the performance of the powder coating prepared by the polyester, and the performance of the powder coating can be obtained by adopting the conventional bi-component dry-mixed powder coating, but the mechanical performance requirement of post-processing forming can not be met; chinese patent CN101445591A discloses a high and low acid value polyester resin for an environment-friendly dry-mixed low-gloss powder coating and a preparation method thereof, the prepared high and low acid value polyester resin has proper glass transition temperature and good storage stability, a powder coating prepared by curing with beta-hydroxyalkylamide has excellent extinction effect and good mechanical property, however, a curing system is beta-hydroxyalkylamide which is not universal with a TGIC system, and according to the description in the embodiment in the application, the backflushing performance is general, and the mechanical property is difficult to meet the complex and variable post-forming processing requirement. Aiming at a TGIC type low acid value system, no extinction powder coating capable of meeting post-forming processing exists at present, the polyester resin for the bending-resistant, easy-to-extinction and low-curing agent dosage powder coating synthesized by the invention can be used for preparing the extinction powder coating by adding the extinction agent into single-component resin, has excellent mechanical property and meets the post-forming processing requirement.
Disclosure of Invention
The invention aims to solve at least one of the technical problems in the prior art and provides a polyester resin, and a powder coating prepared from the polyester resin has excellent bending resistance, and excellent delustering performance and leveling performance.
The invention aims to provide a polyester resin, preferably a bending-resistant, extinction-prone and low-curing-agent-consumption polyester resin for powder coating, which is mainly prepared from components such as polyol, polycarbonate diol, dibasic acid, an acidolysis agent, a capping agent, a catalyst, a curing accelerator, an antioxidant and the like through melt polycondensation. The polyester resin has an acid value of 19-29 mgKOH/g, a melt viscosity of 6000-9000 mPa.s at 200 ℃, a glass transition temperature of 56-65 ℃ and a reactivity of 350-550 s at 180 ℃.
According to an embodiment of the present invention, the polyol accounts for 30% to 45% by weight of the raw material, and is selected from one or a mixture of more of asymmetric diol, symmetric diol, trifunctional polyol and higher-functionality polyol.
According to one embodiment of the invention, the asymmetric dihydric alcohol is one or more selected from 2-methyl-2,4-pentanediol and ethylbutylpropanediol.
According to one embodiment of the invention, the symmetric dihydric alcohol is one or more selected from neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol and hexanediol.
According to an embodiment of the present invention, the tri-functional polyol is selected from one or two of trihydroxymethyl ethane and trihydroxymethyl propane, and the higher-functional polyol is selected from pentaerythritol.
According to one embodiment of the invention, the neopentyl glycol is present in an amount of 5/6 or more of the total mass of the polyol.
According to an embodiment of the present invention, the polycarbonate diol accounts for 0.5 to 10% by weight of the raw material, and further the polycarbonate diol is one or a mixture of several of structures represented by formula 1, wherein R is 1 Is one of n-butyl, n-hexyl and cyclohexyl, R 2 Is one of n-butyl and n-hexyl, and n is more thanEqual to 1.
The amount of the polyol of the present invention is preferably 30% to 40%, more preferably 33% to 38%.
According to an embodiment of the present invention, the polycarbonate diol is one or a mixture of several having a structure of formula 1; the amount thereof is preferably 0.5% to 8%, more preferably 1% to 3%.
According to an embodiment of the present invention, the dibasic acid accounts for 45% to 60% of the raw material by mass, and further, the dibasic acid is selected from one or a mixture of more of terephthalic acid, isophthalic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid.
According to one embodiment of the present invention, the dibasic acid comprises terephthalic acid, wherein the amount of terephthalic acid is 6/7 or more of the total mass of the dibasic acid, and the amount of the dibasic acid is preferably 47 to 58%.
According to an embodiment of the present invention, the acid hydrolysis agent accounts for 8% to 15% of the raw material by mass, and is further selected from one or a mixture of more of isophthalic acid, adipic acid, and trimellitic anhydride, and the amount of the acid hydrolysis agent is preferably 8% to 10%.
According to an embodiment of the present invention, the blocking agent is one or a mixture of more of hexadecanol and octadecanol; the amount thereof is preferably 0.1% to 3%, more preferably 0.5% to 2%.
According to an embodiment of the present invention, the catalyst is one or more of monobutyl tin oxide, dibutyltin dilaurate, monobutyl triisooctoate tin, and phthalate chelate, and the amount thereof is preferably 0.07% to 0.1%.
According to an embodiment of the present invention, the curing accelerator accounts for 0.01% to 0.3% by mass of the raw material, and further, the curing accelerator is one or a mixture of more of triphenyl ethyl phosphine bromide and triphenyl phosphine.
According to an embodiment of the present invention, the antioxidant accounts for 0.2% to 5% of the raw material by mass, and further, the antioxidant is selected from one or a mixture of two of antioxidant 168, antioxidant 1076, antioxidant 1010 and antioxidant 619.
The invention also aims to provide a preparation method of the polyester resin for the bending-resistant extinction-prone low-curing agent dosage powder coating.
The preparation method of the bending-resistant easy-extinction low-curing-agent-dosage polyester resin for the powder coating comprises the following steps of:
(1) Adding the polyol and the polycarbonate diol into a reaction kettle, starting nitrogen protection, heating until the materials are melted, then sequentially adding the dibasic acid and the catalyst, heating to a first temperature, and reacting for 10-13 hours;
(2) Adding the acidolysis agent, and reacting for 2-4 hours at a second temperature; adding the end capping reagent, and reacting at a third temperature for 0.5-2 hours; vacuumizing, and performing polycondensation for 2-4 hours at a fourth temperature; and adding the curing accelerator and the antioxidant, and mixing to obtain the bending-resistant easy-extinction low-dosage polyester resin for the powder coating.
According to an embodiment of the present invention, in the step (1), the first temperature is 235 to 243 ℃, and further, the pre-reaction is performed for 1 to 4 hours at 140 to 180 ℃ in the process of raising the temperature to the first temperature; furthermore, the acid value of the product after the reaction for 10 to 13 hours needs to reach 8 to 12mgKOH/g.
According to an embodiment of the present invention, in the step (2), the second temperature is 225 ℃ to 237 ℃, and the acid value of the product after the reaction at the second temperature for 2 to 4 hours needs to reach 35 mgKOH/g to 45mgKOH/g; further, the third temperature is 220-227 ℃, and further, the acid value of the product after the reaction for 0.5-2 hours at the third temperature needs to reach 30-40 mgKOH/g; further, the fourth temperature is 225-235 ℃, further, the acid value of the product after polycondensation for 2-4 hours at the fourth temperature needs to reach 19-29 mgKOH/g, and the melt viscosity at 200 ℃ reaches 5000-9000 mPa.s.
According to one embodiment of the invention, the preparation method of the polyester resin for the bending-resistant delustering-easy low-curing-agent-consumption powder coating comprises the following steps:
(1) Adding polyalcohol and polycarbonate diol into a reaction kettle according to the proportion, starting nitrogen protection, heating until the materials are melted, then sequentially adding a dibasic acid and a catalyst according to the proportion, gradually starting heating, and reacting for 10-13 hours;
(2) Adding acidolysis agent, and reacting for 2-4 hours under heat preservation; adding a blocking agent, and reacting for 0.5-2 hours under heat preservation; vacuumizing and polycondensing for 2-4 hours; adding a curing accelerator and an antioxidant, stirring for 10-30 minutes, and stopping the reaction to obtain the TGIC type bending-resistant extinction-prone polyester resin for the low-acid-value powder coating.
Wherein, in the heating process of the step (1), the reaction is carried out for 1 to 4 hours at the temperature of between 140 and 180 ℃; when the temperature is increased to 235-243 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction needs to reach 8-12 mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 225-237 ℃, and the acid value after heat preservation needs to reach 35-45 mgKOH/g; the temperature of the mixture is kept at 220-227 ℃ after the end capping agent is added, and the acid value of the mixture after the temperature is kept at 30-40 mgKOH/g; the vacuum temperature is 225-235 ℃, the acid value after vacuum pumping needs to reach 19-29 mgKOH/g, and the melt viscosity reaches 5000-9000 mPa.s at 200 ℃.
The polyester resin for the bending-resistant extinction-easy low-curing-agent-consumption powder coating, which is prepared by the invention, has the following characteristics: the single-component extinction powder coating prepared from the polyester resin for the bending-resistant extinction-prone low-curing-agent-consumption powder coating has excellent mechanical properties and excellent extinction performance and leveling performance;
Detailed Description
The following examples are intended to illustrate the invention and do not limit the scope of the invention. The objectives of the present invention can be achieved by those skilled in the art within the scope of the following disclosure.
The present invention will be described with reference to examples, and Table 1 shows properties of polyester resins of examples 1 to 5 and comparative examples 1 to 2 according to the present invention.
Example 1:
(1) Adding 3465g of neopentyl glycol, 200g of hexanediol, 80g of trimethylolpropane and 100g of polycarbonate-1,6-hexanediol glycol into a reaction kettle according to the proportion, starting nitrogen protection, heating until the materials are molten, then sequentially adding 5330g of terephthalic acid, 100g of adipic acid and 8g of monobutyltin oxide, gradually starting heating, and reacting for 10.5 hours;
(2) Adding 850g of isophthalic acid, and reacting for 3.5 hours under the condition of heat preservation; adding 180g of hexadecanol, and reacting for 1.5 hours under the condition of heat preservation; vacuumizing and polycondensing for 2.5 hours; 6g of triphenyl ethyl phosphonium bromide, 20g of antioxidant 168 and 30g of antioxidant 1076 are added, stirred for 15 minutes, and the reaction is stopped to obtain the TGIC type bending-resistant extinction-prone polyester resin for the low acid value powder coating.
Wherein, in the heating process in the step (1), the reaction is carried out for 2 hours at 140-180 ℃; when the temperature is raised to 238 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction is 10mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 235 ℃, and the acid value after heat preservation is 42.3mgKOH/g; the heat preservation temperature after adding the end capping agent is 226 ℃, and the acid value after heat preservation is 38.3mgKOH/g; the vacuumizing temperature is 228 ℃, the acid value after vacuumizing is 28mgKOH/g, and the melt viscosity reaches 6500mPa.s at 200 ℃.
Example 2:
(1) Adding 3180g of neopentyl glycol, 50g of 2-methyl-2,4-pentanediol, 400g of hexanediol, 90g of trimethylolpropane, 100g of polycarbonate-1,6-hexanediol and 250g of polycarbonate-1,6-hexanediol into a reaction kettle according to the proportion, starting nitrogen protection, heating until the materials are melted, then sequentially adding 5330g of terephthalic acid, 100g of adipic acid and 8g of monobutyltin oxide, gradually starting heating, and reacting for 12 hours;
(2) Adding 850g of isophthalic acid, and reacting for 3 hours under the condition of heat preservation; adding 200g of octadecanol, and reacting for 2 hours under heat preservation; vacuumizing and polycondensing for 2.3 hours; 6g of triphenylphosphine, 20g of antioxidant 168 and 30g of antioxidant 1076 are added and stirred for 20 minutes, and the reaction is stopped to obtain the TGIC type bending-resistant extinction-prone polyester resin for the low acid value powder coating.
Wherein, in the heating process in the step (1), the reaction is carried out for 3.5 hours at 140-180 ℃; when the temperature is raised to 242 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction is 11.5mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 236 ℃, and the acid value after heat preservation is 43mgKOH/g; the temperature of the end capping agent is 221 ℃, and the acid value after heat preservation is 36.5mgKOH/g; the vacuum-pumping temperature is 232 ℃, the acid value after vacuum-pumping is 27mgKOH/g, and the melt viscosity at 200 ℃ reaches 7000mPa.s.
Example 3:
(1) Adding 3490g of neopentyl glycol, 20g of 2-methyl-2,4-pentanediol, 60g of pentaerythritol and 300g of polycarbonate-1,4-butanediol into a reaction kettle according to the ratio, starting nitrogen protection, heating until the materials are molten, sequentially adding 5330g of terephthalic acid and 10g of monobutyl triisooctanoic acid tin, gradually starting heating, and reacting for 11 hours;
(2) Adding 200g of isophthalic acid and 450g of adipic acid, and reacting for 2 hours under heat preservation; adding 60g of hexadecanol, and reacting for 1 hour under the condition of heat preservation; vacuumizing and polycondensing for 2.5 hours; 6g of triphenylphosphine, 20g of antioxidant 168 and 30g of antioxidant 1076 are added and stirred for 10 minutes, and the reaction is stopped to obtain the TGIC type bending-resistant easy-extinction low-acid-value polyester resin for the powder coating.
Wherein, in the heating process in the step (1), the reaction is carried out for 2.5 hours at 140-180 ℃; when the temperature is raised to 240 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction is 8.6mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 226 ℃, and the acid value after heat preservation is 40.9mgKOH/g; the heat preservation temperature after adding the end capping agent is 225 ℃, and the acid value after heat preservation is 32mgKOH/g; the vacuumizing temperature is 234 ℃, the acid value after vacuumizing is 22mgKOH/g, and the melt viscosity at 200 ℃ reaches 5800mPa.s.
Example 4:
(1) Adding 3510g of neopentyl glycol, 200g of hexanediol, 60g of pentaerythritol, 150g of polycarbonate-1,4-butanediol-1,6-hexanediol glycol into a reaction kettle according to the mixture ratio, starting nitrogen protection, heating until the materials are molten, sequentially adding 5100g of terephthalic acid, 200g of isophthalic acid, 200g of adipic acid and 7g of monobutyl triisooctanoic acid tin, gradually starting heating, and reacting for 10 hours;
(2) Adding 580g of isophthalic acid and 150g of adipic acid, and reacting for 3 hours under the condition of heat preservation; adding 100g of octadecanol, and reacting for 1.5 hours under the condition of heat preservation; vacuumizing and polycondensing for 3 hours; 6g of triphenylphosphine, 20g of antioxidant 168 and 30g of antioxidant 1076 are added and stirred for 25 minutes, and the reaction is stopped to obtain the TGIC type bending-resistant extinction-prone polyester resin for the low acid value powder coating.
Wherein, in the heating process in the step (1), the reaction is carried out for 3 hours at 140-180 ℃; when the temperature is raised to 235 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction is 10.9mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 233 ℃, and the acid value after heat preservation is 37.9mgKOH/g; the heat preservation temperature after adding the end capping agent is 227 ℃, and the acid value after heat preservation is 35.5mgKOH/g; the vacuum temperature was 231 ℃ and the acid value after vacuum was 22mgKOH/g, and the melt viscosity at 200 ℃ reached 7000mPa.s.
Example 5:
(1) 3490g of neopentyl glycol, 10g of 2-methyl-2,4-pentanediol, 200g of hexanediol, 60g of pentaerythritol, 30g of polycarbonate-1,4-butanediol glycol and 170g of polycarbonate-1,4-butanediol-1,6-hexanediol are added into a reaction kettle according to the proportion, nitrogen protection is started, the temperature is raised until the materials are melted, then 5120g of terephthalic acid, 210g of isophthalic acid, 200g of adipic acid and 7g of monobutyl triisooctanoic acid tin are sequentially added, the temperature is gradually raised, and the reaction is carried out for 11.8 hours;
(2) 560g of isophthalic acid and 150g of adipic acid are added, and the reaction is carried out for 3.2 hours under the condition of heat preservation; adding 30g of octadecanol, and reacting for 0.5 hour under heat preservation; vacuumizing and polycondensing for 3.5 hours; 6g of triphenyl ethyl phosphonium bromide, 20g of antioxidant 168 and 30g of antioxidant 1076 are added and stirred for 30 minutes, and the reaction is stopped to obtain the TGIC type bending-resistant extinction-prone polyester resin for the low acid value powder coating.
Wherein, in the heating process in the step (1), the reaction is carried out for 2.8 hours at 140-180 ℃; when the temperature is raised to 238 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction is 11.2mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 236 ℃, and the acid value after heat preservation is 39.9mgKOH/g; the heat preservation temperature after adding the end capping agent is 222 ℃, and the acid value after heat preservation is 37.8mgKOH/g; the vacuumizing temperature is 233 ℃, the acid value after vacuumizing is 25mgKOH/g, and the melt viscosity reaches 8300mPa.s at 200 ℃.
Comparative example 1:
(1) Adding 3145g of neopentyl glycol, 500g of hexanediol and 60g of pentaerythritol into a reaction kettle according to the ratio, starting nitrogen protection, heating to melt the materials, sequentially adding 5100g of terephthalic acid, 200g of isophthalic acid and 8g of monobutyl tin oxide, gradually starting heating, and reacting for 12 hours;
(2) 775g of isophthalic acid is added, and the reaction is carried out for 3.8 hours under the condition of heat preservation; vacuumizing and polycondensing for 3 hours; 6g of triphenylethylphosphonium bromide, 20g of antioxidant 168 and 30g of antioxidant 1076 were added, and the reaction was stopped by stirring for 30 minutes to obtain a polyester resin of comparative example 1.
Wherein, in the heating process of the step (1), the reaction is carried out for 3 hours at the temperature of 140-180 ℃; when the temperature is raised to 242 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction is 9.9mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 237 ℃, and the acid value after heat preservation is 43.6mgKOH/g; the vacuumizing temperature is 234 ℃, the acid value after vacuumizing is 28mgKOH/g, and the melt viscosity reaches 7800mPa.s at 200 ℃.
Comparative example 2:
(1) Adding 3560g of neopentyl glycol and 80g of trimethylolpropane into a reaction kettle according to the proportion, starting nitrogen protection, heating until the materials are molten, sequentially adding 5100g of terephthalic acid, 150g of adipic acid and 8g of monobutyl triisooctanoic acid tin, gradually starting heating, and reacting for 12.2 hours;
(2) Adding 330g of isophthalic acid and 300g of adipic acid, and reacting for 2.8 hours under the condition of heat preservation; vacuumizing and polycondensing for 3.5 hours; 6g of triphenylethylphosphonium bromide, 20g of antioxidant 168 and 30g of antioxidant 1076 were added, and the reaction was stopped by stirring for 15 minutes to obtain a polyester resin of comparative example 2.
Wherein, in the heating process in the step (1), the reaction is carried out for 2 hours at 140-180 ℃; when the temperature is raised to 239 ℃, the heat preservation reaction is needed, and the acid value after the heat preservation reaction is 8.7mgKOH/g; the heat preservation temperature after adding the acidolysis agent in the step (2) is 229 ℃, and the acid value after heat preservation is 37.4mgKOH/g; the vacuumizing temperature is 230 ℃, the acid value after vacuumizing is 22mgKOH/g, and the melt viscosity reaches 6500mPa.s at 200 ℃.
The indexes or properties of the polyester resins prepared by the methods of examples 1 to 5 and comparative examples 1 to 2 were measured according to international standards or methods commonly used in the industry, and the results are shown in table 1, wherein the acid value, viscosity and glass transition temperature were measured according to the T/GDTL 004-2019 standard, and the reactivity at 180 ℃ was measured according to the T/GDTL 004-2019 standard.
TABLE 1 Properties of polyester resins
The polyester resins prepared according to the methods of examples 1 to 5 and comparative examples 1 to 2 were applied to powder coatings, respectively, and the powder coatings and the corresponding coatings were prepared as follows: polyester resin, curing agent TGIC, titanium dioxide, barium sulfate, flatting agent, benzoin and brightener are uniformly mixed according to a formula proportion, and are subjected to tabletting, freezing and crushing, sieving and electrostatic spraying by a double-screw extruder. Meanwhile, the coatings prepared according to the above method were subjected to performance tests according to national standards or methods commonly used in the industry, and the results are shown in Table 2, wherein gloss was measured according to the regulations of GB/T9754-2007, using a 60 ° incident angle, impact was measured according to the T/GDTL 004-2019 standard, T bend was measured according to the NCCA II-19 standard, horizontal flow was measured according to the GB 6554-1986 standard, surface appearance was measured according to visual inspection, and hand touch was measured.
TABLE 2 composition and coating Properties of the powder coatings
As shown in Table 2, the bending-resistant extinction-easy polyester resin for powder coating, which is prepared by the formula and the process of the invention and used by the low curing agent dosage, has excellent mechanical properties when used for powder coating, and simultaneously has good extinction property and leveling property. In addition, the powder coatings prepared using the polyester resins of the formulations of comparative examples 1 and 2 did not perform as well as the powder coatings formed using the polyester resins for the bend resistant, matable, low curing agent dosage powder coatings of the present invention.
The components listed in the invention, the upper limit, the lower limit and the interval value of the components can realize the invention, and the embodiment is not listed. The present invention is illustrated by a part of specific examples, and it should be noted that the upper and lower specific examples are only used for further illustration of the present invention, and do not represent a limitation to the scope of the present invention, and the polyester resin provided by the present invention is not limited to the field of post-molding processing. Other insubstantial modifications and adaptations of the present invention can be made without departing from the scope of the present invention.
Claims (17)
1. The polyester resin for the bending-resistant extinction-prone low-curing-agent-dosage powder coating is characterized by comprising the following components in parts by weight: the polyester resin has an acid value of 19-29 mgKOH/g, melt viscosity of 6000-9000 mPa.s at 200 ℃, glass transition temperature of 56-65 ℃ and reactivity of 350-550 s at 180 ℃, and is mainly prepared by carrying out melt polycondensation on the following raw materials: polyol, polycarbonate diol, dibasic acid, acidolysis agent, capping agent, catalyst, curing accelerator and antioxidant;
the polyol accounts for 30-45% of the raw material by mass and is selected from one or a mixture of more of asymmetric dihydric alcohol, symmetric dihydric alcohol, trifunctional polyol and higher functionality polyol;
the asymmetric dihydric alcohol is selected from one or a mixture of more of 2-methyl-2,4-pentanediol and ethyl butyl propanediol;
the symmetrical dihydric alcohol is one or a mixture of more of neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol and hexanediol;
the polyol comprises neopentyl glycol, the neopentyl glycol constituting 5/6 or more of the total mass of the polyol;
the polycarbonate diol accounts for 0.5 to 10 percent of the raw material by mass;
the dibasic acid accounts for 45-60% of the raw materials by mass;
the acidolysis agent accounts for 8-15% of the raw materials by mass;
the end-capping reagent accounts for 0.1 to 5 percent of the mass of the raw material;
the catalyst accounts for 0.01 to 0.5 percent of the mass of the raw material;
the curing accelerator accounts for 0.01-0.3% of the raw materials by mass;
the antioxidant accounts for 0.2 to 5 percent of the mass of the raw material;
2. the polyester resin for powder coating of claim 1, wherein the polyester resin is characterized by comprising: the tri-functionality polyol is selected from one or two of trihydroxymethyl ethane and trihydroxymethyl propane.
3. The polyester resin for powder coating with bending resistance, easy extinction and low curing agent dosage according to claim 1, wherein: the higher functionality polyol is selected from pentaerythritol.
4. The polyester resin for powder coating material with bending resistance, easy extinction and low curing agent content as claimed in claim 1, wherein: the polycarbonate diol is one or a mixture of several of structures shown as a formula 1, wherein R 1 Is one of n-butyl, n-hexyl and cyclohexyl, R 2 Is one of n-butyl and n-hexyl, and n is an integer of a repeating unit;
5. the polyester resin for powder coating of claim 1, wherein the polyester resin is characterized by comprising: the dibasic acid is selected from one or a mixture of more of terephthalic acid, isophthalic acid, adipic acid and 1,4-cyclohexanedicarboxylic acid.
6. The polyester resin for powder coating material with bending resistance, easy extinction and low curing agent content as claimed in claim 5, wherein: the dibasic acid comprises terephthalic acid, and the terephthalic acid accounts for 6/7 or more of the total mass of the dibasic acid.
7. The polyester resin for powder coating material with bending resistance, easy extinction and low curing agent content as claimed in claim 1, wherein: the acidolysis agent is one or a mixture of more of isophthalic acid, adipic acid and trimellitic anhydride.
8. The polyester resin for powder coating of claim 1, wherein the polyester resin is characterized by comprising: the end capping agent is one or a mixture of more of hexadecanol and octadecanol.
9. The polyester resin for powder coating with bending resistance, easy extinction and low curing agent dosage according to claim 1, wherein: the catalyst is one or a mixture of more of monobutyl tin oxide, dibutyltin dilaurate, monobutyl triisooctoate tin and phthalate ester chelate.
10. The polyester resin for powder coating of claim 1, wherein the polyester resin is characterized by comprising: the curing accelerator is one or a mixture of more of triphenyl ethyl phosphonium bromide and triphenyl phosphine.
11. The polyester resin for powder coating with bending resistance, easy extinction and low curing agent dosage according to claim 1, wherein: the antioxidant is selected from one or a mixture of two of antioxidant 168, antioxidant 1076, antioxidant 1010 and antioxidant 619.
12. The process for preparing a polyester resin for powder coating of any one of claims 1 to 11, which is resistant to bending and easy to deluster and has low curing agent content, wherein the polyester resin comprises: the method comprises the following steps:
(1) Adding the polyalcohol and the polycarbonate diol into a reaction kettle, starting nitrogen protection, heating until the materials are melted, then sequentially adding the dibasic acid and the catalyst, heating to a first temperature, and reacting for 10-13 hours;
(2) Adding the acidolysis agent, and reacting at a second temperature for 2-4 hours; adding the end-capping reagent, and reacting at a third temperature for 0.5-2 hours; vacuumizing, and polycondensing for 2-4 hours at a fourth temperature; and adding the curing accelerator and the antioxidant, and mixing to obtain the bending-resistant easy-extinction low-dosage polyester resin for the powder coating.
13. The method for preparing the polyester resin for the powder coating with bending resistance, easy extinction and low curing agent dosage according to claim 12, is characterized in that: in the step (1), the first temperature is 235-243 ℃.
14. The method for preparing the polyester resin for the powder coating with bending resistance, easy extinction and low curing agent dosage according to claim 12, is characterized in that: and in the process of heating to the first temperature, pre-reaction is carried out for 1 to 4 hours at the temperature of between 140 and 180 ℃.
15. The method for preparing the polyester resin for the powder coating with bending resistance, easy extinction and low curing agent dosage according to claim 12, is characterized in that: the acid value of the product after 10 to 13 hours of reaction needs to reach 8 to 12mgKOH/g.
16. The process for preparing a polyester resin for a bending-resistant matted powder coating using a low amount of a curing agent as claimed in claim 12, wherein: in the step (2), the second temperature is 225-237 ℃.
17. The process for preparing a polyester resin for a bending-resistant matted powder coating using a low amount of a curing agent as claimed in claim 12, wherein: the acid value of the product after polycondensation for 2 to 4 hours at the fourth temperature needs to reach 19 to 29mgKOH/g, and the melt viscosity reaches 5000 to 9000mPa.s at 200 ℃.
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| JP2008174636A (en) * | 2007-01-18 | 2008-07-31 | Sanyo Chem Ind Ltd | Polyester resin for powder coating |
| CN105061741A (en) * | 2015-09-08 | 2015-11-18 | 常州华科聚合物股份有限公司 | Water-boiling-resistant polyester resin and preparation method thereof |
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| JP2008174636A (en) * | 2007-01-18 | 2008-07-31 | Sanyo Chem Ind Ltd | Polyester resin for powder coating |
| CN105061741A (en) * | 2015-09-08 | 2015-11-18 | 常州华科聚合物股份有限公司 | Water-boiling-resistant polyester resin and preparation method thereof |
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