CN112048235A

CN112048235A - Long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating and preparation method thereof

Info

Publication number: CN112048235A
Application number: CN202010951582.7A
Authority: CN
Inventors: 陈君; 徐友楼; 鲍文鑫; 吴有军
Original assignee: Anhui Xinyou Polymer New Material Technology Co ltd
Current assignee: Anhui Xinyou Polymer New Material Technology Co ltd
Priority date: 2020-09-11
Filing date: 2020-09-11
Publication date: 2020-12-08
Anticipated expiration: 2040-09-11
Also published as: CN112048235B

Abstract

The invention belongs to the technical field of preparation of polyester powder coatings, and particularly relates to a long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating and a preparation method thereof. The powder coating of the invention comprises the following main raw materials: 560 parts of polyester resin 530-. The polyester resin used in the powder coating has a good linear structure, and ensures excellent flow property; the powder coating uses more trifunctional curing agent TGIC, and is matched with trimesic acid triglycidyl ester with low melting point and excellent water resistance to serve as a low-temperature curing agent, so that the crosslinking density and the water resistance of a coating film are further improved, and the long-acting weather resistance and the chlorine salt corrosion resistance are finally ensured. The final powder coating product can be used for low-temperature curing at 160 ℃, and the prepared coating film has good long-acting weather resistance and chloride corrosion resistance, and is particularly suitable for spraying infrastructure of highways, such as guardrails, bridges and the like.

Description

Long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating and preparation method thereof

Technical Field

The invention belongs to the technical field of preparation of polyester powder coatings, and particularly relates to a long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating and a preparation method thereof.

Background

The powder coating contains no organic solvent, 100 percent of solid components, has the advantages of no pollution, energy and resource saving, high mechanical strength of the coating film, complete recovery of excessive coating and the like compared with the conventional coating, and is more and more widely applied to coating of building shells of household appliances, automobile industry, outdoor bridges, highway guardrails and the like.

In winter, in order to prevent icing and ensure the smoothness of a highway, a large amount of snow-melting agent needs to be broadcast, but the main varieties of the snow-melting agent at home and abroad at present are chloride salt type products, such as sodium chloride, magnesium chloride, calcium chloride and the like, because the broadcast range of a broadcast broadcaster is wide, the snow-melting agent needs to be broadcast in the whole winter, the broadcast time is long, the solubility of the snow-melting agent is high, the corrosion of the highway guardrail and metal bridges is serious, the maintenance and the replacement of the highway guardrail and the metal bridges are not easy, and outdoor long-acting weather-proof and corrosion-resistant powder coating aiming at the corrosion of the conventional chloride salt, such as sodium chloride, magnesium chloride and calcium chloride, needs to be developed.

The powder coating has the advantages of small chloride ion molecules, strong permeability, long duration in winter, no pinholes, strong hydrophobic property of the surface of the coating film, excellent adhesion between the coating film and a base material and good weather resistance, and needs to realize thick coating on the surface of the coating film.

CN110256943A discloses a graphene modified super-weather-resistant powder coating, which is characterized in that: the powder coating comprises the following raw materials in parts by weight: 40-60 parts of polyester resin, 1-5 parts of TGIC curing agent, 18-22 parts of barium sulfate, 1-3 parts of mica powder, 1-2 parts of polytetrafluoroethylene wax, 1-3 parts of flatting agent, 1-2 parts of wetting agent, 10-18 parts of rutile titanium dioxide, 1-5 parts of weather-resistant pigment and 3-5 parts of graphene modified aging resistant agent. The perfect combination of the polyester resin, the graphene modified aging resistant agent and the auxiliary agent can improve the weather resistance by doubling.

The powder coating has low crosslinking density and poor water and inorganic salt penetration resistance, and the aim of improving the weather resistance is mainly achieved by adopting the matching of the graphene modified anti-aging agent and the polyester resin, so that the problems of the traditional expressway guardrails and bridges cannot be solved, and the technical problems of the weather resistance and the chloride corrosion resistance by improving the polyester resin are rarely disclosed in documents.

Disclosure of Invention

In order to solve the technical problems, the invention provides a long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating prepared from special polyester resin;

the powder coating is prepared from the following main raw materials:

560 parts of polyester resin 530-;

the polyester resin is prepared by polycondensation of the following main materials in parts by mole at high temperature: 3-8 parts of tetrafluorosuccinic anhydride, 12-22 parts of adipic acid, 7-15 parts of diglycidyl terephthalate, 10-20 parts of neopentyl glycol, 6-13 parts of diglycidyl cyclohexane-1, 2-dicarboxylate and 9-18 parts of isophthalic acid.

The polyester resin adopts a polyester synthesis catalyst during preparation, wherein the polyester synthesis catalyst is monobutyl tin oxide, and the dosage of the polyester synthesis catalyst is 0.1-0.3% of the total mass of the main materials.

The polyester resin also adopts antioxidant tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, and the dosage of the antioxidant tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester is 0.2-0.5 percent of the total mass of the main materials.

The polyester resin adopted in the invention has the following preparation steps:

(1) adding the neopentyl glycol with the formula amount into a reaction kettle, heating to melt the neopentyl glycol, adding the tetrafluorosuccinic anhydride and the monobutyl tin oxide with the formula amount for polymerization reaction, heating and carrying out heat preservation reaction;

(2) when the acid value of the polymer is lower than 15mgKOH/g, adding adipic acid and diglycidyl terephthalate according to the formula amount, heating and preserving heat to continue the polymerization reaction;

(3) when the acid value of the polymer in the step (2) is lower than 120mgKOH/g, cooling, adding the cyclohexane-1, 2-dicarboxylic acid diglycidyl ester according to the formula amount, and continuing the heat preservation reaction;

(4) when the acid value of the polymer is less than or equal to 40mgKOH/g, the temperature is raised at the speed of 15-20 ℃/h, the antioxidant with the formula amount is added, and the linear macromolecular polyester is promoted to be formed through vacuum reaction;

(5) and (3) stopping vacuumizing when the acid value of the polymer in the step (4) is less than or equal to 18mgKOH/g, then adding a capping agent isophthalic acid with a formula amount to perform carboxyl capping reaction, heating and preserving heat for reaction, stopping reaction when the acid value reaches 48-53mgKOH/g, discharging at high temperature while the reaction is hot, cooling, and then crushing and granulating to obtain the polyester resin.

Preferably, the preparation steps of the polyester resin are as follows:

(1) adding neopentyl glycol with the formula amount into a reaction kettle, heating to 135 ℃ for sufficient melting, adding tetrafluorosuccinic anhydride and monobutyltin oxide with the formula amount for polymerization reaction, gradually heating to 180 ℃ at the speed of 10-12 ℃/h, and then carrying out heat preservation reaction for 1-3 h;

(2) when the acid value of the polymer is lower than 15mgKOH/g, adding adipic acid and diglycidyl terephthalate with the formula amount, continuing the polymerization reaction, heating to 220 ℃ at the speed of 5-7 ℃/h, and carrying out heat preservation reaction for 2-5 h;

(3) when the acid value of the polymer in the step (2) is lower than 120mgKOH/g, the temperature is reduced to 180-190 ℃, then the cyclohexane-1, 2-dicarboxylic acid diglycidyl ester with the formula amount is added, and the heat preservation reaction is continued for 3-6 h;

(4) when the acid value of the polymer is less than or equal to 40mgKOH/g, heating to 200-205 ℃ at the speed of 15-20 ℃/h, adding the antioxidant with the formula amount, starting a vacuum system to keep the vacuum degree between-0.095 MPa and-0.098 MPa, and carrying out vacuum reaction at 200-205 ℃ for 1-3h to promote the formation of linear macromolecular polyester;

(5) and (3) stopping vacuumizing when the acid value of the polymer in the step (4) is less than or equal to 18mgKOH/g, then adding a formula amount of end capping agent isophthalic acid to perform carboxyl end capping reaction, heating to 230 ℃ at the speed of 8-10 ℃/h, performing heat preservation reaction for 2-4h, stopping reaction when the acid value reaches 48-53mgKOH/g, discharging at high temperature when the temperature is hot, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the polyester resin.

The preparation method of the long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating provided by the invention comprises the following steps:

s1: melting TGIC and triglycidyl trimesate according to the formula amount, and mixing and reacting to obtain a modified curing agent;

s2: mixing the modified curing agent with the formula amount and the polyester resin at a high speed;

s3: melting and extruding the mixed material in the step S2, and crushing to obtain a primary extruded material;

s4: weighing the primary extrusion material in the S3 and other materials in the powder coating formula, adding the weighed materials into a high-speed mixer, starting a mixing device, and mixing at a high speed;

s5: after the materials in the S4 are uniformly mixed, adding the materials into a double-screw extruder for melt extrusion;

s6: conveying the material melt-extruded by the double-screw extruder to a tablet press with a tap water cooling system for tabletting and coarse crushing into granules;

s7: and grinding the coarse particles by using a mill, and screening out and collecting target particles by using an induced air system of the mill to obtain the finished powder coating.

Preferably, in S1, the melting reaction temperature is 105-110 ℃, and after the melting is completed, the stirring is carried out to ensure that the mixing reaction time is about 25-35min, based on the full melting of the materials.

Preferably, in S2, the high speed mixing is carried out for about 15-30 min.

Preferably, in S3, the extrusion section temperature is 120 ℃ and 130 ℃, and the screw rotation speed is 500 rpm and 570 rpm.

Preferably, the preparation method of the long-acting weather-resistant and chlorine salt corrosion-resistant polyester powder coating comprises the following steps:

s1: adding TGIC and triglycidyl trimesate in a formula amount into a reaction kettle, gradually heating to 100-105 ℃, stirring after the materials are completely melted to allow the materials to react for 25-35min, discharging when the materials are hot, cooling and crushing into 50-80 meshes to obtain modified curing agent powder;

s2, weighing the modified curing agent powder obtained in the step S1 and the polyester resin according to the formula ratio, adding the modified curing agent powder and the polyester resin into a high-speed mixer, starting a mixing device, and mixing for 15-30min at a high speed;

s3, after the main raw materials in the S2 are mixed uniformly, adding the mixture into a double-screw extruder for melt extrusion, wherein the temperature of an extrusion section is 120 ℃ plus 130 ℃, and the rotating speed of a screw is 500 plus 570 rpm; then cooling and crushing the mixture into particles with the particle size of 2-5mm to obtain a primary extruded material;

s4, adding the primary extrusion material obtained in the step S3, titanium dioxide, barium sulfate, a brightener and a leveling agent into a high-speed mixer, starting a mixing device, and mixing at high speed for 15-30 min;

s5: after the main raw materials in the S4 are uniformly mixed, adding the mixture into a double-screw extruder for melt extrusion, wherein the temperature of an extrusion section is 130-;

s7: and grinding the coarse particles by a mill, and screening out the particles of 140 meshes and 160 meshes by an induced air system of the mill for collection to obtain the finished powder coating.

The invention has the beneficial effects that:

(1) the adopted polyester resin is obtained by polymerizing the raw materials of tetrafluorosuccinic anhydride, adipic acid, diglycidyl terephthalate, neopentyl glycol, cyclohexane-1, 2-dicarboxylic acid diglycidyl ester and isophthalic acid, has good linear structure and low softening point, ensures excellent low-temperature flow property, and can realize thick coating without pinholes;

(2) fluorine is introduced into the polyester chain segment, so that the characteristic of strong hydrophobic capability of the polyester chain segment is fully utilized, and the hydrophobic effect of the product is exerted;

(3) the diglycidyl terephthalate and the diglycidyl cyclohexane-1, 2-dicarboxylate are adopted to participate in the reaction, so that a certain amount of hydroxyl groups are distributed in a polyester chain segment, the adhesion with a base material is greatly improved, the penetration of chloride ions can be prevented for a long time, and the weather resistance is outstanding.

(4) The acid value of the polyester resin obtained by the invention is higher and reaches 48-53mgKOH/g, more three-functionality curing agent TGIC and triglycidyl trimesate are needed to be used in the powder coating, the triglycidyl trimesate has the advantages of low melting range (65-72 ℃) and high curing activity, and after being mixed with TGIC, the mixture is firstly subjected to primary melting extrusion with the polyester resin to obtain a uniform primary cross-linked mixture, and then is subjected to secondary melting extrusion with various auxiliaries to obtain a coating film capable of being cured at low temperature. The cured coating has high crosslinking density and good water resistance, and finally ensures long-acting weather resistance and chlorine salt corrosion resistance. The coating film prepared by the final powder coating product has good long-acting weather resistance and chlorine salt corrosion resistance, can be used for spraying infrastructure of highways such as guardrails, bridges and the like, and achieves the effects of long-acting corrosion resistance and weather resistance.

Detailed Description

The present invention will now be further described with reference to specific embodiments in order to enable those skilled in the art to better understand the present invention.

The main raw materials of the powder coating are as follows:

560 parts of polyester resin 530-; the parts are parts by weight;

the polyester resin comprises the following main materials in parts by mole: 3-8 parts of tetrafluorosuccinic anhydride, 12-22 parts of adipic acid, 7-15 parts of diglycidyl terephthalate, 10-20 parts of neopentyl glycol, 6-13 parts of diglycidyl cyclohexane-1, 2-dicarboxylate and 9-18 parts of isophthalic acid; the catalyst is monobutyl tin oxide, and the using amount of the catalyst is 0.1-0.3% of the total mass of the main materials; antioxidant tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, the dosage of which is 0.2-0.5 percent of the total mass of the main materials (antioxidant 1010);

example 1

The preparation method of the long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating comprises the following steps:

s1: adding TGIC and triglycidyl trimesate in a formula amount into a reaction kettle, gradually heating to 107 ℃, stirring after the materials are completely melted to mix and react for 30min, discharging while hot, cooling and crushing into 60 meshes to obtain modified curing agent powder;

s2, weighing the modified curing agent powder obtained in the step S1 and the polyester resin according to the formula ratio, adding the modified curing agent powder and the polyester resin into a high-speed mixer, starting a mixing device, and mixing at high speed for about 20 min;

s3, after the main raw materials in the S2 are mixed uniformly, adding the mixture into a double-screw extruder for melt extrusion, wherein the temperature of an extrusion section is about 125 ℃, and the rotating speed of a screw is 545 rpm; then cooling and crushing the mixture into particles with the diameter of 4mm to obtain a primary extruded material;

s4, adding the primary extrusion material obtained in the step S3, titanium dioxide, barium sulfate, a brightener and a leveling agent into a high-speed mixer, starting a mixing device, and mixing at high speed for 20 min; the rotating speed of the high-speed mixing is 6000 r/min;

s5: after the main raw materials in the S4 are uniformly mixed, adding the mixture into a double-screw extruder for melt extrusion, wherein the extrusion section temperature is 135 ℃, and the screw rotation speed is 535 rpm;

s7: grinding the coarse particles by a mill, screening out 150-mesh particles by an induced air system of the mill, and collecting to obtain the finished powder coating.

The polyester resin in the step S1 is prepared by polycondensation of the following main materials in parts by mole at high temperature, and the preparation steps of the polyester resin are as follows:

(2) when the acid value of the polymer is lower than 15mgKOH/g, adding adipic acid and diglycidyl terephthalate with the formula amount, continuing the polymerization reaction, heating to 220 ℃ at the speed of about 6 ℃/h, and carrying out heat preservation reaction for 4 h;

(3) when the acid value of the polymer in the step (2) is lower than 120mgKOH/g, cooling to 185 ℃, adding the cyclohexane-1, 2-dicarboxylic acid diglycidyl ester according to the formula amount, and continuing to perform heat preservation reaction for 5 hours;

(4) when the acid value of the polymer is less than or equal to 40mgKOH/g, heating to about 205 ℃ at the rate of 18 ℃/h, adding the antioxidant with the formula amount, starting a vacuum system to keep the vacuum degree between-0.095 Mpa and-0.098 Mpa, and carrying out vacuum reaction at the temperature of about 203 ℃ for 2h to promote the formation of linear macromolecular polyester;

(5) and (3) stopping vacuumizing when the acid value of the polymer in the step (4) is less than or equal to 18mgKOH/g, then adding a capping agent isophthalic acid with a formula amount to perform carboxyl capping reaction, heating to 228 ℃ at the speed of 9 ℃/h, preserving heat for reaction for 3h, stopping reaction when the acid value reaches 48-53mgKOH/g, discharging at high temperature while the polyester resin is hot, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the polyester resin, wherein the appearance of the polyester resin is colorless and transparent particles.

In examples 2 to 4, the raw material ratio of the polyester resin was slightly different from that of example 1, and the following were specifically mentioned:

TABLE 1 Main raw materials (parts by weight) of powder coatings in examples 1 to 4

TABLE 2 Main raw materials for the raw polyester resins of examples 1 to 4

Note: in Table 2, the monobutyl tin oxide and antioxidant 1010 are both referred to as percentages of the total raw materials used in the preparation of the polyester resin.

TABLE 3 acid value and softening point of the raw material polyester resins of examples 1 to 4

	Example 1	Example 2	Example 3	Example 4
					Acid value (mgKOH/g)	50	48	53	51
Softening Point (. degree. C.)	101	102	105	99

Comparative example 1: the commercial common outdoor TGIC system powder coating is purchased from Gallery red lion powder coating Co., Ltd, the model is RAL9006 (special for guard rails), the film thickness is about 120 mu m, and the curing conditions are as follows: 200 ℃/15 min.

Example 5

Preparing a coating layer: and spraying the prepared powder coating on the galvanized iron substrate subjected to surface treatment by using an electrostatic spray gun, wherein the film thickness is about 120 mu m, and fully curing at 160 ℃/20min to obtain the coating.

The detection of the coating index is based on GB/T21776 2008 'Standard guide for powder coating and coating detection'; weather resistance test the artificial weathering test was carried out continuously for 700h according to the procedures of the specified steps A in Table 4 of GB/T1865-2009 xenon arc radiation for artificial weathering of colored paint and varnish and exposure and filtration of artificial radiation. The adhesion rating is in accordance with GB/T9286 1998 test of marking test of paint films of colored paint and varnish; the chlorine salt corrosion resistance is realized by adopting a soaking method, after the coating is respectively soaked in a chlorine salt solution with the mass concentration of 20% for 168 hours at room temperature, the surface is lightly washed clean by running water, and the conditions of color change, bubbling, cracking and falling of the surface of the coating are observed; the salt spray test is carried out according to GB/1771-2007 determination of neutral salt spray resistance of colored paint and varnish, a test plate is placed in a salt spray box at an angle of 15-25 degrees, and the result is observed after 600 hours;

TABLE 4 Performance testing of examples and comparative examples

As can be seen from the properties in the above tables, the powder coatings in examples 1-4 have smooth appearance, no pinholes and excellent impact resistance; the glossiness is high, and no change or obvious change exists in the test investigation of weather resistance within 700 hours; simultaneously, the paint has good chlorine salt corrosion resistance; the salt spray resistance performance is examined and has no change under 600 hours;

in comparative example 1, the appearance was substantially flat with a small number of pinholes, and the appearance showed significant loss of gloss in a weathering test of 700 hours; and in 20% NaCl solution, 20% MgCl solution, 20% CaCl₂Obvious phenomena of light loss, slight bubbling and the like appear after 168 hours of treatment in the solution; in addition, table for salt spray resistance performance examination at 600 hoursShowing slight loss of gloss and minimal blistering.

Compared with the similar product, the product of the invention has more remarkable advantages in weather resistance and chlorine salt corrosion resistance compared with the similar product, namely comparative example 1.

Claims

1. The long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating is characterized by being prepared from the following main raw materials:

560 parts of polyester resin 530-; the parts are by weight;

2. The long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating as claimed in claim 1, wherein the polyester resin is prepared by using a polyester synthesis catalyst, and the polyester synthesis catalyst is monobutyl tin oxide, and the dosage of the polyester synthesis catalyst is 0.1-0.3% of the total mass of the main materials.

3. The long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating according to any one of claims 1 or 2, wherein the polyester resin is prepared by using an antioxidant of tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester in an amount of 0.2-0.5% of the total mass of the main materials.

4. The long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating as claimed in claim 3, wherein said polyester resin is prepared by the steps of:

5. The long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating as claimed in claim 1, wherein the polyester resin is prepared by the steps of:

(4) when the acid value of the polymer is less than or equal to 40mgKOH/g, heating to 200-205 ℃ at the speed of 15-20 ℃/h, adding the antioxidant with the formula amount, starting a vacuum system to keep the vacuum degree between-0.098 MPa and-0.095 MPa, and carrying out vacuum reaction at 200-205 ℃ for 1-3h to promote the formation of linear macromolecular polyester;

6. The method of preparing the long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating of claim 1, comprising the steps of:

s2, mixing the modified curing agent with the polyester resin at high speed;

s3, melting and extruding the mixed material in the step S2, and crushing to obtain a primary extruded material;

s4, weighing the primary extrusion material in the S3 and other materials in the powder coating formula, adding the weighed materials into a high-speed mixer, starting a mixing device, and mixing at a high speed;

7. The method according to claim 6, wherein in S1, the temperature of the melting reaction is 105-110 ℃; and in S2, mixing at high speed for 15-30 min.

8. The method as claimed in claim 6, wherein in S3, the temperature of the extrusion section is 120-130 ℃, and the screw speed is 500-570 rpm.

9. The method of preparing the long-acting weather-resistant chlorine salt corrosion-resistant polyester powder coating of claim 6, comprising the steps of:

s1: adding TGIC and triglycidyl trimesate in a formula amount into a reaction kettle, gradually heating to 105-110 ℃, stirring to mix and react after materials are completely melted, discharging while hot, cooling and crushing into 50-80 meshes to obtain modified curing agent powder;