CN111909363B

CN111909363B - Polyester resin for high-temperature-resistant and solvent-resistant matte powder coating and preparation method thereof

Info

Publication number: CN111909363B
Application number: CN202010863518.3A
Authority: CN
Inventors: 汪云端; 梁优莲; 刘春容
Original assignee: Huangshan Jiaheng Technology Co ltd
Current assignee: Huangshan Jiaheng Technology Co ltd
Priority date: 2020-08-25
Filing date: 2020-08-25
Publication date: 2022-08-19
Anticipated expiration: 2040-08-25
Also published as: CN111909363A

Abstract

The invention belongs to the technical field of polyester resin production, and particularly relates to a high-temperature-resistant and solvent-resistant polyester resin for matte powder coating. The polyester resin comprises the following main raw materials in parts by mole: 10-15 parts of p-xylylene dimethyl ether; 15-24 parts of phenol; 5-8 parts of succinic anhydride; 20-30 parts of pyridine; 1, 6-dihydroxyhexane 8-15; 9-18 parts of hexahydrophthalic anhydride; 3, 7-dimethyl-1, 7-octanediol 6-12; 5-9 parts of isophthalic acid. The invention has the beneficial effects that a specific method is adopted, such as that the p-xylylene dimethyl ether and phenol are reacted under the catalytic action of anhydrous aluminum trichloride to obtain micromolecule polyphenol ether resin, then succinic anhydride is added to carry out phenol esterification reaction to obtain the micromolecule polyphenol ether resin grafted with carboxyl, and then the micromolecule polyphenol ether resin is polymerized with 1, 6-dihydroxyhexane, hexahydrophthalic anhydride, 3, 7-dimethyl-1, 7-octanediol and isophthalic acid, so that the obtained product has excellent high temperature resistance and solvent resistance.

Description

Polyester resin for high-temperature-resistant and solvent-resistant matte powder coating and preparation method thereof

Technical Field

The invention belongs to the technical field of polyester resin production, and particularly relates to a high-temperature-resistant and solvent-resistant polyester resin for matte powder coating.

Background

In the common polyester resin powder coating, polyester resin is mostly formed by polymerizing common dibasic acid and dihydric alcohol, the high temperature resistance of raw materials per se is poor, the crosslinking density of a cured coating is low, the high temperature resistance and the solvent resistance are poor, and if a matte coating with excellent decoration (the gloss is 15-30%) is to be obtained, a flatting agent is additionally used, so that the problems of poor flatting stability and complex preparation are caused, and the high temperature resistant, solvent resistant and matte coating can be simultaneously obtained without the existing polyester resin product.

For example, the powder coating disclosed in CN110964180A can obtain 5-7% of low gloss and excellent dulling performance under the condition of adding a dulling agent. "in this document, it is necessary to add a matting agent to obtain a low gloss of 5 to 7%.

Therefore, the polyester resin for matte powder coating, which has high temperature resistance and excellent solvent resistance, and the preparation method thereof need to be developed in order to overcome the defects.

Disclosure of Invention

In order to solve the technical problems, the invention provides a polyester resin for matte powder coating, which has high temperature resistance and excellent solvent resistance;

the invention also provides a preparation method of the polyester resin;

the polyester resin for the matte powder coating and the preparation method thereof have the advantages that dimethyl terephthalate and phenol are reacted under the catalytic action of anhydrous aluminum trichloride to obtain micromolecule polyphenol ether resin, then succinic anhydride is added to carry out phenol esterification reaction to obtain the micromolecule polyphenol ether resin grafted with carboxyl, and the micromolecule polyphenol ether resin is polymerized with 1, 6-dihydroxyhexane, hexahydrophthalic anhydride, 3, 7-dimethyl-1, 7-octanediol and isophthalic acid to obtain the polyester resin.

The finally obtained polyester resin molecular chain segment contains the polyphenol ether resin with excellent high temperature resistance and solvent resistance, the curing and film forming process is carried out by adopting a double curing agent mode, the surface gloss of the finally coated film is lower due to the difference of curing speeds, the gloss is basically 15-25%, the high temperature resistance of the coated film can reach 250 ℃/12h and 320 ℃/2h without obvious change on the basis that the basic mechanical property can be met, and the conventional solvent resistance is also excellent.

The polyester resin for the high-temperature-resistant and solvent-resistant matte powder coating provided by the invention comprises the following main raw materials in parts by mole:

10-15 parts of p-xylylene dimethyl ether; 15-24 parts of phenol; 5-8 parts of succinic anhydride; 20-30 parts of pyridine; 1, 6-dihydroxyhexane 8-15; 9-18 parts of hexahydrophthalic anhydride; 3, 7-dimethyl-1, 7-octanediol 6-12; 5-9 parts of isophthalic acid;

the catalyst also comprises other auxiliary agents, wherein the auxiliary agents comprise a first catalyst, a second catalyst, a third catalyst and an antioxidant;

a first catalyst: anhydrous aluminum trichloride, the amount of which is 0.8-1.5% of the mass of the p-xylylene dimethyl ether;

a second catalyst: 4-dimethylamino pyridine, the amount of which is 2-4% of the mass of the succinic anhydride;

a third catalyst: monobutyl tin oxide, the amount is 0.1-0.2% of the total mass of the raw materials;

the antioxidant is preferably 1010, namely tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, and the dosage of the antioxidant is 0.3-0.5 percent of the total mass of the raw materials.

The preparation method of the polyester resin provided by the invention comprises the following steps:

A. adding p-xylylene dimethyl ether, phenol and a first catalyst into a reaction kettle I, heating for polymerization reaction, continuing heating after no obvious methanol is distilled out of the system, starting a vacuum system at the same time, and removing unreacted micromolecule raw materials under reduced pressure to obtain polyphenol ether resin;

B. cooling, adding pyridine, mixing and dissolving, adding a second catalyst 4-dimethylamino pyridine and succinic anhydride to perform phenol esterification reaction, keeping the temperature for reaction, stopping the reaction when the succinic anhydride participating in the reaction reaches more than 96%, removing the pyridine solvent under reduced pressure to obtain the succinic anhydride grafted polyphenylether resin,

cooling to room temperature, and crushing into particles;

C. adding 1, 6-dihydroxyhexane, hexahydrophthalic anhydride and a third catalyst of tin monobutyloxide into a reaction kettle II, heating and preserving heat for esterification dehydration reaction, then adding half of the mass of the succinic anhydride grafted polyphenol ether resin obtained in the step B, heating again and preserving heat for reaction;

D. when the acid value of the polymer in the step C is reduced to 110mgKOH/g, adding 3, 7-dimethyl-1, 7-octanediol and the other half of the mass of the succinic anhydride grafted polyphenol ether resin obtained in the step B, gradually heating and keeping the temperature for reaction until no obvious distillate is evaporated, wherein the acid value of a reactant is less than 30 mgKOH/g;

E. then adding an antioxidant, starting a vacuum system, continuing the reaction, and stopping the vacuum system when the acid value is reduced to be below 10 mgKOH/g;

F. cooling, adding isophthalic acid for end-capping reaction, heating and preserving heat for reaction, stopping reaction when the acid value of the reactant is 15-20mgKOH/g, discharging at high temperature while the reactant is hot, cooling, and crushing and granulating to obtain the final product polyester resin.

Preferably, the method of the invention comprises the steps of:

A. adding the p-xylylene dimethyl ether, the phenol and the first catalyst anhydrous aluminum trichloride into a reaction kettle I according to the formula amount, heating to 135-plus 145 ℃ for carrying out full polymerization for 4-6h, continuing heating to 160-plus 170 ℃ after no obvious methanol is distilled out of the system, starting a vacuum system at the same time, keeping the vacuum degree between-0.095 Mpa and-0.098 Mpa, and removing unreacted micromolecular raw materials under reduced pressure to obtain the polyphenol ether resin;

B. then cooling to 100-110 ℃, adding pyridine with the formula amount for mixing and dissolving, then adding a second catalyst 4-dimethylamino pyridine with the formula amount and succinic anhydride for phenol esterification reaction, carrying out heat preservation reaction at 110 ℃ for 3-5h, stopping the reaction when the succinic anhydride participating in the reaction reaches more than 96%, removing the pyridine solvent under reduced pressure to obtain succinic anhydride grafted polyphenylene ether resin, cooling to room temperature, and crushing into particles with 30-50 meshes;

C. adding 1, 6-dihydroxyhexane, hexahydrophthalic anhydride and a third catalyst, namely monobutyltin oxide, into a reaction kettle II according to the formula ratio, heating to 180 ℃, carrying out heat preservation esterification dehydration reaction for 1-2h, then adding half of the mass of the succinic anhydride grafted polyphenylether resin obtained in the step B, gradually heating to 200 ℃ at the heating rate of 10 ℃/h, and carrying out heat preservation reaction for 2-4 h;

D. when the acid value of the polymer in the step C is reduced to 110mgKOH/g, adding 3, 7-dimethyl-1, 7-octanediol with the formula amount and the other half of the mass of the succinic anhydride grafted polyphenol ether resin obtained in the step B, gradually heating to 230 ℃ at the speed of 5-7 ℃/h, and carrying out heat preservation reaction for 2-5h until no obvious distillate is evaporated, wherein the acid value of a reactant is less than 30 mgKOH/g;

E. adding an antioxidant 1010, starting a vacuum system, keeping the vacuum degree between-0.095 Mpa and-0.098 Mpa, continuously reacting for 1-3h, and stopping the vacuum system when the acid value is reduced to below 10 mgKOH/g;

F. when the temperature is reduced to 200 ℃, adding the isophthalic acid with the formula amount for end-capping reaction, heating to 230 ℃ at the speed of 6-8 ℃/h, continuing to perform heat preservation reaction for 2-4h, stopping the reaction when the acid value of the reactant is 15-20mgKOH/g, discharging at high temperature while the reactant is hot, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the final product of the polyester resin.

The product obtained by the preparation method has colorless and transparent particles in appearance; the acid value is 15-20mgKOH/g, and the softening point is 100-110 ℃.

The invention has the beneficial effects that the adopted specific method comprises the steps of firstly using dimethyl terephthalate and phenol to react under the catalytic action of anhydrous aluminum trichloride to obtain micromolecular polyphenol ether resin, then adding succinic anhydride to carry out phenol esterification reaction to obtain micromolecular polyphenol ether resin grafted with carboxyl, and then polymerizing the micromolecular polyphenol ether resin with 1, 6-dihydroxyhexane, hexahydrophthalic anhydride, 3, 7-dimethyl-1, 7-octanediol and isophthalic acid, so that the obtained product has excellent high temperature resistance and solvent resistance.

Detailed Description

The present invention will now be further described with reference to specific embodiments in order to provide a better understanding of the invention to those skilled in the art.

The polyester resin for the matte powder coating, which has high temperature resistance and excellent solvent resistance, comprises the following main raw materials in parts by mole:

10-15 parts of p-xylylene dimethyl ether

Phenol 15-24

Succinic anhydride 5-8

Pyridine 20-30

1, 6-dihydroxyhexane 8-15

Hexahydrophthalic anhydride 9-18

3, 7-dimethyl-1, 7-octanediol 6-12

Isophthalic acid 5-9

The catalyst for synthesizing the polyphenol ether resin is anhydrous aluminum trichloride, and the using amount of the catalyst is 0.8-1.5 percent of the total mass of the raw material of the p-xylylene dimethyl ether; (hereinafter referred to as a first catalyst);

the phenol esterification catalyst is 4-dimethylamino pyridine (DMAP), and the using amount of the phenol esterification catalyst is 2-4% of the mass of the succinic anhydride; (hereinafter referred to as a second catalyst);

the chain extension esterification catalyst is monobutyl tin oxide, and the using amount of the chain extension esterification catalyst is 0.1-0.2% of the total mass of the raw materials; (hereinafter referred to as a third catalyst);

the antioxidant is 1010, namely tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, and the using amount of the antioxidant is 0.3-0.5 percent of the total mass of the raw materials.

Example 1

The proportions of the raw materials in example 1 are shown in table 1; the polyester resin in example 1 was prepared as follows:

A. adding the p-xylylene dimethyl ether, the phenol and the first catalyst anhydrous aluminum trichloride into a reaction kettle I according to the formula amount, heating to 135-plus 145 ℃ for full polymerization reaction for 4-6h, continuing heating to 160-plus 170 ℃ after no obvious methanol is distilled from the system, simultaneously starting a vacuum system, keeping the vacuum degree between-0.095 Mpa and-0.098 Mpa, and removing unreacted micromolecular raw materials under reduced pressure to obtain the polyphenol ether resin;

B. then cooling to 100-;

F. when the temperature is reduced to 200 ℃, adding the isophthalic acid with the formula amount for end-capping reaction, heating to 230 ℃ at the speed of 6-8 ℃/h, continuing to perform heat preservation reaction for 2-4h, stopping the reaction when the acid value of the reactant is 15-20mgKOH/g, discharging at high temperature while the reactant is hot, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the final product of the polyester resin. (in other embodiments, on the basis of embodiment 1, the parameters of the reaction conditions are selected within the above-mentioned range, for example, the reaction is performed under heat preservation for 2-4 hours, or performed for 3 hours or 3.5 hours according to actual conditions, and then, for example, the temperature is decreased to 110 ℃ and actually decreased to 102 ℃, 108 ℃ or 105 ℃, so as to satisfy the reaction conditions in the interval defined in embodiment 1).

The methods of examples 2 to 4 are the same as example 1, and the molar ratios of the raw materials are shown in Table 1:

TABLE 1 amounts of raw materials used for the products of examples 1-4

	Example 1	Example 2	Example 3	Example 4
					Dimethyl Ether P	10	14	12	15
Phenol and its preparation	15	22	20	24
					Succinic anhydride	5	7	6	8
Pyridine compound	20	23	25	30
					1, 6-dihydroxyhexane	8	11	12	15
Hexahydrophthalic anhydride	9	12	14	18
					3, 7-dimethyl-1, 7-octanediol	6	10	9	12
Isophthalic acid	5	6	7	9
					First catalyst (%)	0.8	1.2	1.0	1.5
Second catalyst (%)	2	3.5	3	4
					Third catalyst (%)	0.1	0.18	0.15	0.2
Antioxidant agent	0.3	0.45	0.4	0.5

(note: in Table 1, the amount of anhydrous aluminum trichloride serving as a first catalyst is the percentage of the total mass of the raw material p-xylylene dimethyl ether, the amount of 4-dimethylaminopyridine serving as a second catalyst is the percentage of the mass of succinic anhydride, the amount of monobutyltin oxide serving as a third catalyst is the percentage of the total mass of the raw material, and the antioxidant is the percentage of the total mass of the main raw material, wherein the main raw material refers to other raw materials except auxiliary materials).

The acid values and softening points of the products of examples 1-4 are shown in Table 2 below:

TABLE 2 acid number and softening point of the products of examples 1 to 4

	Example 1	Example 2	Example 3	Example 4
					Acid value (mgKOH/g)	16	18	17	20
Softening Point (. degree. C.)	109	106	104	101

Example 5

In this embodiment, a dual curing system is used to cure the products of embodiments 1 to 4, and the formula of the powder coating comprises the following components in parts by weight:

preparing a coating layer: and uniformly mixing the materials according to the formula of the curing system powder coating, extruding, tabletting and crushing by using a double-screw extruder, and then crushing and sieving the tablets to prepare the powder coating. The powder coating is sprayed on the galvanized iron substrate after surface treatment by an electrostatic spray gun, the film thickness is about 80 mu m, and the powder coating is fully cured at 200 ℃/20min, thus obtaining the coating.

Comparative example 1: polyester resin for commercial common TGIC system, acid value: 35mgKOH/g, softening point 108 ℃, model SJ4C, purchased from New Material Ltd of Shenjian, Anhui. The TGIC powder coating formula matched with the polyester resin in the industry is adopted for coating preparation of the powder coating, the film thickness is about 80 mu m, and the curing conditions are as follows: 200 ℃/10 min.

The detection of the coating index is based on GB/T21776-2008 'Standard guide for detecting powder coating and coating thereof'; the high temperature resistance is carried out according to GB/T1735-2009 determination of heat resistance of colored paint and varnish; the performance of the conventional solvent resistance is realized by adopting a dropping method, 5 drops of the test solvent are respectively dropped on the surface of the coating film at room temperature, and the condition that the surface of the coating film is discolored or bubbled is observed after 6 hours (if the condition that the solvent is volatilized exists, the solvent is timely dripped at the position of the original dropping liquid).

TABLE 3 Performance testing of examples and comparative examples

As can be seen from the data in Table 3, after the products in examples 1-4 are applied, the film appearance is flat and the front and back sides pass through; the gloss (60 DEG angle) is only 16.5-22.4; in the high-temperature performance test, the high-temperature resistance time at 250 ℃ is as long as 20 hours, and even after 20 hours, the appearance is not changed; no significant change after 2 hours at 320 ℃; the performance of methanol, acetone and toluene resistance is good.

The powder coating film prepared from the similar commercial polyester resin product in the comparative example 1 has unsatisfactory high temperature resistance and solvent resistance, and shows obvious yellowing at high temperature and a phenomenon of light loss or bubbling in a solvent.

Claims

1. The polyester resin for the high-temperature-resistant and solvent-resistant matte powder coating is characterized by comprising the following main raw materials in parts by mole:

a first catalyst: anhydrous aluminum trichloride, the dosage of which is 0.8 to 1.5 percent of the mass of the p-xylylene dimethyl ether;

the antioxidant is tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, and the using amount of the antioxidant is 0.3-0.5 percent of the total mass of the raw materials;

the preparation method of the polyester resin comprises the following steps:

B. cooling, adding pyridine, mixing and dissolving, then adding a second catalyst, namely 4-dimethylaminopyridine and succinic anhydride, to perform a phenol esterification reaction, performing a heat preservation reaction, stopping the reaction when the content of succinic anhydride participating in the reaction reaches more than 96%, removing the pyridine solvent under reduced pressure to obtain succinic anhydride grafted polyphenol ether resin, cooling to room temperature, and crushing into particles;

C. adding 1, 6-dihydroxyhexane, hexahydrophthalic anhydride and a third catalyst of monobutyltin oxide into a reaction kettle II, heating and preserving heat to carry out esterification dehydration reaction, then adding half of the mass of the succinic anhydride grafted polyphenol ether resin obtained in the step B, heating again and preserving heat to carry out reaction;

2. The polyester resin as claimed in claim 1, wherein A, the formula amount of the dimethyl ether terephthalate, the phenol and the first catalyst anhydrous aluminum trichloride are added into a reaction kettle I, the temperature is raised to 135-145 ℃ for full polymerization reaction for 4-6h, after no obvious methanol is distilled out of the system, the temperature is continuously raised to 160-170 ℃, simultaneously, a vacuum system is started, the vacuum degree is kept between-0.095 MPa and-0.098 MPa, and the unreacted small molecular raw materials are removed under reduced pressure to obtain the polyphenol ether resin.

3. The polyester resin as claimed in claim 1, wherein B is cooled to 100-110 ℃, pyridine with the formula amount is added for mixing and dissolving, then a second catalyst 4-Dimethylaminopyridine (DMAP) with the formula amount and succinic anhydride are added for phenol esterification reaction, the reaction is stopped when the succinic anhydride participating in the reaction reaches more than 96 percent, the pyridine solvent is removed under reduced pressure to obtain the succinic anhydride grafted polyphenylether resin, and the resin is cooled to room temperature and crushed into particles with 30-50 meshes.

4. The polyester resin according to claim 1, wherein C, 1, 6-dihydroxyhexane, hexahydrophthalic anhydride and a third catalyst of monobutyltin oxide are added into a reaction kettle II according to the formula, the temperature is increased to 180 ℃, the esterification dehydration reaction is kept for 1-2h, then half of the mass of the succinic anhydride grafted polyphenylether resin obtained in the step B is added, the temperature is gradually increased to 200 ℃ at the temperature increasing rate of 10 ℃/h, and the heat preservation reaction is kept for 2-4 h.

5. The polyester resin according to claim 1, wherein D, when the acid value of the polymer in the step C is reduced to 110mgKOH/g, the formula amount of 3, 7-dimethyl-1, 7-octanediol and the other half of the mass of the succinic anhydride grafted polyphenol ether resin obtained in the step B are added, the temperature is gradually increased to 230 ℃ at the rate of 5-7 ℃/h, and the reaction is kept for 2-5h until no obvious distillate is distilled off, and the acid value of the reactant is less than 30 mgKOH/g.

6. The polyester resin according to claim 1, wherein E, antioxidant 1010 is added, a vacuum system is started, the vacuum degree is kept between-0.095 Mpa and-0.098 Mpa, the reaction is continued for 1 to 3 hours, and the vacuum system is stopped when the acid value is reduced to below 10 mgKOH/g.

7. The polyester resin according to claim 1, wherein F, when the temperature is reduced to 200 ℃, the isophthalic acid with the formula amount is added for end-capping reaction, the temperature is increased to 230 ℃ at 6-8 ℃/h, the reaction is continued for 2-4h under heat preservation, when the acid value of the reactant is 15-20mgKOH/g, the reaction is stopped, the material is discharged at high temperature, the polyester resin is cooled by a steel belt with condensed water, and then the polyester resin is crushed and granulated to obtain the final product polyester resin.

8. The polyester resin according to claim 1, wherein the preparation method of the polyester resin comprises the steps of:

B. then cooling to 100-;

C. adding 1, 6-dihydroxyhexane, hexahydrophthalic anhydride and a third catalyst, namely monobutyl tin oxide, into a reaction kettle II according to the formula ratio, heating to 180 ℃, carrying out heat preservation esterification dehydration reaction for 1-2h, then adding half of the mass of the succinic anhydride grafted polyphenol ether resin obtained in the step B, gradually heating to 200 ℃ at the heating rate of 10 ℃/h, and carrying out heat preservation reaction for 2-4 h;