阅读说明：本技术 一种持久耐高温及硬度优的粉末涂料用聚酯树脂及制备方法 (Polyester resin with lasting high temperature resistance and excellent hardness for powder coating and preparation method thereof ) 是由 周勇 吴泽凯 洪昭武 汪利华 谭卫东 李海云 于 2020-11-20 设计创作，主要内容包括：公开了一种持久耐高温及硬度优的粉末涂料用聚酯树脂及制备方法。该聚酯树脂主要使用苯酚、腰果酚、甲醛、硼酸、六氢邻苯二甲酸酐、新戊二醇、季戊四醇、己二酸等作为原料来进行反应,最终得到酸值在38-45mgKOH/g的产品。该聚酯树脂采用特殊的小分子耐高温硼酚醛树脂与六氢邻苯二甲酸酐等进行扩链、再酯化聚合得到。其与TGIC固化后的涂膜持久耐高温性能好且硬度高,可以达到260℃/96h下几乎无变化,且硬度达到3H以上,涂膜表观、抗冲击、耐沸水煮等性能也均达到粉末涂料的应用要求。(Discloses a polyester resin with lasting high temperature resistance and excellent hardness for powder coating and a preparation method thereof. The polyester resin is prepared by reacting phenol, cardanol, formaldehyde, boric acid, hexahydrophthalic anhydride, neopentyl glycol, pentaerythritol, adipic acid and the like which are mainly used as raw materials, and finally obtaining a product with an acid value of 38-45 mgKOH/g. The polyester resin is obtained by chain extension and esterification polymerization of special micromolecule high temperature resistant boron phenolic resin and hexahydrophthalic anhydride and the like. The coating film after TGIC curing has good lasting high temperature resistance and high hardness, can almost not change at 260 ℃/96H, has hardness of more than 3H, and has the properties of coating film appearance, impact resistance, boiling water boiling resistance and the like which meet the application requirements of powder coating.)

1. A preparation method of polyester resin for powder coating with lasting high temperature resistance and excellent hardness comprises the following raw materials in parts by mole:

2. the method for preparing polyester resin according to claim 1, wherein the catalyst is monobutyl tin oxide in an amount of 0.05-0.1% of the total molar amount of raw materials excluding the catalyst and the pH adjustor.

3. The method for producing a polyester resin according to claim 1, wherein the formaldehyde is an aqueous formaldehyde solution having a formaldehyde concentration of 32 to 37% by mass.

4. The method for preparing polyester resin according to claim 1, wherein the method for preparing polyester resin further comprises the steps of:

A. adding phenol, cardanol and formaldehyde in a formula amount into a reactor, stirring, heating to 80-85 ℃, adding a pH regulator to regulate the pH value of the system to 2-3, and controlling the reaction temperature to be 80-85 ℃ for heat preservation reaction;

B. when the viscosity of the reaction mixture reaches 2000-2500mpa & s (25 ℃), adding boric acid with the formula amount for reaction, starting a vacuum system, gradually heating to 130-135 ℃ in a negative pressure state, and continuously carrying out heat preservation reaction;

C. after no material is evaporated within 1min, closing the vacuum system, adding hexahydrophthalic anhydride and a catalyst according to the formula amount, heating to a certain temperature, and carrying out heat preservation reaction;

D. when the acid value of the reaction mixture reaches 150-165mgKOH/g, neopentyl glycol and pentaerythritol in the formula amount are added, and then the temperature is raised to a certain temperature for heat preservation reaction;

E. when the acid value of the polymer is 30-45mgKOH/g, starting a vacuum system to perform vacuum polycondensation;

F. stopping the vacuum system when the acid value of the polymer reaches 15-20mgKOH/g, adding adipic acid with the formula amount, and heating to 235-240 ℃ for end-capping reaction;

G. stopping the reaction when the acid value of the polymer reaches 38-45mgKOH/g, discharging, cooling, crushing and granulating to obtain the polyester resin for the powder coating.

5. The method for preparing polyester resin according to claim 4, wherein the degree of vacuum of negative pressure in step B or E is-0.097 MPa to-0.099 MPa.

6. The method for preparing polyester resin according to claim 4, wherein in the step C, the temperature is gradually increased to 190-195 ℃ at a temperature increasing rate of 8-10 ℃/h.

7. The method for preparing polyester resin according to claim 4, wherein in the step D, the temperature is gradually increased to 225-230 ℃ at a temperature increasing rate of 6-8 ℃/h.

8. The polyester resin for powder coating prepared by the preparation method according to claims 1 to 7.

9. The polyester resin for powder coating according to claim 8, wherein the polyester resin has a softening point of 115-125 ℃.

10. A powder coating comprising the polyester resin for powder coating according to claim 8 or 9.

Technical Field

The invention belongs to the field of powder coating, and relates to polyester resin for powder coating and a preparation method thereof.

Background

The powder coating has the characteristics of no solvent, 100 percent film forming and almost no emission, and has become the environmental-friendly coating direction of the national key development.

With the application and development of industrial large-scale drying equipment such as high-temperature drying rooms, large-scale baking ovens for workshops and the like, the requirements on durable high-temperature-resistant coatings such as polyester powder coatings are high. Moreover, the fields are placed indoors, so that slight rubbing is easy to occur when transferring and drying material products, the coating film is damaged, and obvious scratches or dents appear. Therefore, it is desired that the coating film has high hardness to have a function of resisting physical damage while achieving a high temperature resistance.

Current polyester resins for high temperature resistant powder coatings are modified with silicones, such as ZL 201610625455.1. The polyester resin obtained by modifying the organosilicon intermediate improves the high-temperature resistance of the coating to a certain extent, but the hardness of the coating is greatly reduced due to relatively small molecules of the organosilicon resin, so that the organosilicon resin cannot be used in the fields with high temperature resistance and high requirements on hardness.

Therefore, a new polyester resin for powder coating is needed to solve the above technical problems.

Disclosure of Invention

In order to solve the technical problems, the invention provides a polyester resin for powder coating with lasting high temperature resistance and excellent hardness and a preparation method thereof.

The invention provides a preparation method of polyester resin for powder coating with lasting high temperature resistance and excellent hardness, which comprises the following raw materials in parts by mole:

a catalyst, and

a pH regulator.

Wherein the catalyst is monobutyl tin oxide, and the dosage of the monobutyl tin oxide is 0.05-0.1 percent of the total molar weight of raw materials without the catalyst and the pH regulator;

wherein the formaldehyde is a formaldehyde aqueous solution with the formaldehyde mass concentration of 32-37% (preferably 35%).

Wherein the pH regulator is hydrochloric acid solution with mass concentration of 25-35% (preferably 31%).

Wherein, the preparation method of the polyester resin also comprises the following steps:

A. adding phenol, cardanol and formaldehyde in a formula amount into a reactor, stirring, heating to 80-85 ℃, adding a pH regulator to regulate the pH value of the system to 2-3, and controlling the reaction temperature to be 80-85 ℃ for heat preservation reaction;

B. when the viscosity of the reaction mixture reaches 2000-2500mpa & s (25 ℃), adding boric acid with the formula amount for reaction, starting a vacuum system, gradually heating to 130-135 ℃ in a negative pressure state, and continuously carrying out heat preservation reaction;

C. after no material is evaporated within 1min, closing the vacuum system, adding hexahydrophthalic anhydride and a catalyst according to the formula amount, heating to a certain temperature, and carrying out heat preservation reaction;

D. when the acid value of the reaction mixture reaches 150-165mgKOH/g, neopentyl glycol and pentaerythritol in the formula amount are added, and then the temperature is raised to a certain temperature for heat preservation reaction;

E. when the acid value of the polymer is 30-45mgKOH/g, starting a vacuum system to perform vacuum polycondensation;

F. stopping the vacuum system when the acid value of the polymer reaches 15-20mgKOH/g, adding adipic acid with the formula amount, and heating to 235-240 ℃ for end-capping reaction;

G. stopping the reaction when the acid value of the polymer reaches 38-45mgKOH/g, discharging, cooling, crushing and granulating to obtain the polyester resin for the powder coating.

Wherein in the step B, the negative pressure vacuum degree is between-0.097 MPa and-0.099 MPa.

Wherein, in the step C, the temperature is gradually increased to 190-195 ℃ at a temperature increasing rate of 8-10 ℃/h.

Wherein, in the step D, the temperature is gradually increased to 225 ℃ and 230 ℃ at a temperature increasing speed of 6-8 ℃/h.

Wherein, in the step E, the vacuum degree is between-0.097 MPa and-0.099 MPa.

And G, discharging at high temperature while the material is hot.

In the step G, the cooling is to cool the resin by using a steel belt with condensed water.

Wherein, the reactor is a reaction kettle.

The invention also provides the polyester resin for the powder coating prepared by the preparation method.

The polyester resin is light yellow transparent particles in appearance, and has an acid value of 38-45mgKOH/g and a softening point of 115-125 ℃.

The invention also provides a powder coating which comprises the polyester resin for the powder coating.

The beneficial technical effects of the invention are embodied in the following aspects:

1. the polyester resin for powder coating is prepared by reacting phenol, cardanol, formaldehyde, boric acid, hexahydrophthalic anhydride, neopentyl glycol, pentaerythritol, adipic acid and the like as raw materials to finally obtain the polyester resin with the acid value of 38-45 mgKOH/g.

2. The polyester resin is obtained by chain extension and re-esterification polymerization of special micromolecule high temperature resistant boron phenolic resin, hexahydrophthalic anhydride and the like, the molecular structure contains more boron phenolic resin structures, the high temperature resistance is good, the functionality is high, a coating film cured with TGIC (triglycidyl isocyanurate) has good lasting high temperature resistance and high hardness, almost no change can be achieved at 260 ℃/96H, the hardness reaches more than 3H, and other properties such as coating film appearance, impact resistance, boiling water boiling resistance, adhesive force and the like all meet the application requirements of powder coatings.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

A preparation method of polyester resin for powder coating with lasting high temperature resistance and excellent hardness comprises the following raw materials in parts by mole:

the preparation method comprises the following steps:

A. adding phenol, cardanol and formaldehyde in a formula amount into a reaction kettle, starting stirring, heating to 85 ℃, adding concentrated hydrochloric acid solution to adjust the pH value of the system to 2, and controlling the reaction temperature to 85 ℃ for heat preservation reaction;

B. when the viscosity of the reaction mixture reaches 2450Mpa · s (25 ℃), adding boric acid with the formula amount for reaction, starting a vacuum system, keeping the vacuum degree at-0.098 Mpa, gradually heating to 135 ℃, and continuously preserving heat for reaction;

C. after no material is evaporated within 1min, closing the vacuum system, adding hexahydrophthalic anhydride and catalyst monobutyl tin oxide according to the formula amount, then gradually heating to 190 ℃ at the heating rate of 10 ℃/h, and continuing the heat preservation reaction;

D. when the acid value of the reaction mixture reaches 155mgKOH/g, neopentyl glycol and pentaerythritol in the formula amount are added, then the temperature is gradually increased to 230 ℃ at the temperature increase speed of 6 ℃/h, and the reaction is carried out in a heat preservation way;

E. when the acid value of the polymer is 45mgKOH/g, starting a vacuum system, keeping the vacuum degree at-0.097 Mpa, and carrying out vacuum polycondensation;

f, stopping the vacuum system when the acid value of the polymer reaches 16mgKOH/g, adding adipic acid with the formula amount, and heating to 235 ℃ for end capping reaction;

G. and stopping the reaction when the acid value of the polymer reaches 41mgKOH/g, discharging at high temperature while the polymer is hot, cooling the resin by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin for the powder coating.

The acid value of the prepared polyester resin is 41mgKOH/g, the softening point is 116 DEG C

Example 2

A preparation method of polyester resin for powder coating with lasting high temperature resistance and excellent hardness comprises the following raw materials in parts by mole:

the preparation method comprises the following steps:

A. adding phenol, cardanol and formaldehyde in a formula amount into a reaction kettle, starting stirring, heating to 85 ℃, adding concentrated hydrochloric acid solution to adjust the pH value of the system to 3, and controlling the reaction temperature to 85 ℃ for heat preservation reaction;

B. when the viscosity of the reaction mixture reaches 2030Mpa & s (25 ℃), adding boric acid with the formula amount for reaction, starting a vacuum system, keeping the vacuum degree at-0.097 Mpa, gradually heating to 130 ℃, and continuously preserving heat for reaction;

C. after no material is evaporated within 1min, closing the vacuum system, adding hexahydrophthalic anhydride and catalyst monobutyl tin oxide according to the formula amount, then gradually heating to 190 ℃ at the heating rate of 8 ℃/h and continuing the heat preservation reaction;

D. when the acid value of the reaction mixture reaches 164mgKOH/g, adding neopentyl glycol and pentaerythritol in a formula amount, then gradually heating to 225 ℃ at a heating rate of 8 ℃/h, and carrying out heat preservation reaction;

E. when the acid value of the polymer is 36mgKOH/g, starting a vacuum system, keeping the vacuum degree at-0.098 Mpa, and carrying out vacuum polycondensation;

f, stopping the vacuum system when the acid value of the polymer reaches 20mgKOH/g, adding adipic acid with the formula amount, and heating to 240 ℃ for end-capping reaction;

G. and stopping the reaction when the acid value of the polymer reaches 39mgKOH/g, discharging at high temperature while the polymer is hot, cooling the resin by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin for the powder coating.

The acid value of the prepared polyester resin is 39mgKOH/g, the softening point is 119 DEG C

Example 3

A preparation method of polyester resin for powder coating with lasting high temperature resistance and excellent hardness comprises the following raw materials in parts by mole:

the preparation method comprises the following steps:

A. adding phenol, cardanol and formaldehyde in a formula amount into a reaction kettle, starting stirring, heating to 85 ℃, adding concentrated hydrochloric acid solution to adjust the pH value of the system to 2.5, and controlling the reaction temperature to 85 ℃ for heat preservation reaction;

B. when the viscosity of the reaction mixture reaches 2370Mpa · s (25 ℃), adding boric acid with the formula amount for reaction, starting a vacuum system, keeping the vacuum degree at-0.099 Mpa, gradually heating to 132 ℃, and continuously preserving heat for reaction;

C. after no material is evaporated within 1min, closing the vacuum system, adding hexahydrophthalic anhydride and catalyst monobutyl tin oxide according to the formula amount, then gradually heating to 193 ℃ at the heating rate of 9 ℃/h and continuing the heat preservation reaction;

D. when the acid value of the reaction mixture reaches 151mgKOH/g, adding neopentyl glycol and pentaerythritol in a formula amount, then gradually heating to 228 ℃ at a heating rate of 7 ℃/h, and carrying out heat preservation reaction;

E. when the acid value of the polymer is 39mgKOH/g, starting a vacuum system, keeping the vacuum degree at-0.099 Mpa, and carrying out vacuum polycondensation;

f, stopping the vacuum system when the acid value of the polymer reaches 17mgKOH/g, adding adipic acid with the formula amount, and heating to 237 ℃ for end capping reaction;

G. and stopping the reaction when the acid value of the polymer reaches 45mgKOH/g, discharging at high temperature while the polymer is hot, cooling the resin by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin for the powder coating.

The acid value of the prepared polyester resin is 45mgKOH/g, the softening point is 124 DEG C

Example 4

A preparation method of polyester resin for powder coating with lasting high temperature resistance and excellent hardness comprises the following raw materials in parts by mole:

the preparation method comprises the following steps:

A. adding phenol, cardanol and formaldehyde in a formula amount into a reaction kettle, starting stirring, heating to 85 ℃, adding concentrated hydrochloric acid solution to adjust the pH value of the system to 2.7, and controlling the reaction temperature to 85 ℃ for heat preservation reaction;

B. when the viscosity of the reaction mixture reaches 2210Mpa · s (25 ℃), adding boric acid with the formula amount for reaction, starting a vacuum system, keeping the vacuum degree at-0.098 Mpa, gradually heating to 134 ℃, and continuously preserving heat for reaction;

C. after no material is evaporated within 1min, closing the vacuum system, adding hexahydrophthalic anhydride and catalyst monobutyl tin oxide according to the formula amount, then gradually heating to 191 ℃ at the heating rate of 10 ℃/h and continuing the heat preservation reaction;

D. when the acid value of the reaction mixture reaches 159mgKOH/g, neopentyl glycol and pentaerythritol in the formula amount are added, then the temperature is gradually increased to 226 ℃ at the temperature increase speed of 6 ℃/h, and the reaction is carried out in a heat preservation way;

E. when the acid value of the polymer is 31mgKOH/g, starting a vacuum system, keeping the vacuum degree at-0.097 Mpa, and carrying out vacuum polycondensation;

f, stopping the vacuum system when the acid value of the polymer reaches 15mgKOH/g, adding adipic acid with the formula amount, and heating to 236 ℃ for end capping reaction;

G. and stopping the reaction when the acid value of the polymer reaches 40mgKOH/g, discharging at high temperature while the polymer is hot, cooling the resin by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin for the powder coating.

The acid value of the prepared polyester resin is 40mgKOH/g, the softening point is 121 DEG C

Comparative example 1

The product of example 1 in ZL201610625455.1 was used as comparative example 1 in place of the polyester resin of the present invention.

Comparative example 2

The polyester resin of the present invention was replaced with a commercially available conventional TGIC powder coating as comparative example 2, available from Guanghua science and technology, Zhejiang, under model number GH-2200.

The polyester resins prepared in examples 1 to 4 and the polyester resins of comparative examples 1 to 2 were prepared into TGIC curable powder coatings according to the following formulations by weight and tested for their application properties.

The powder coating formula comprises:

preparation of powder coating:

the materials are uniformly mixed according to the formula of the powder coating, are extruded at low temperature (the temperature of a screw is controlled at 130-. The powder coating is sprayed on the galvanized iron substrate after surface treatment by adopting an electrostatic spray gun and is solidified at the temperature of 200 ℃/10min to obtain a coating layer with the film thickness of 70-80 mu m.

The application performance of the powder coating is detected, and the test method comprises the following steps:

the detection of the coating index is carried out according to the standard GB/T21776 and 2008 'detection standard guideline for powder coating and coating thereof';

the hardness test is carried out according to the standard GB/T6739-;

the high temperature resistance test is carried out according to the method of GB/T1735-2009 determination of heat resistance of colored paint and varnish, the temperature is 260 ℃, and the time is 96 hours;

the gasoline resistance test is carried out according to the method A (gasoline immersion method) in the standard GB/T1734-1993 'paint film gasoline resistance determination method', and No. 120 solvent oil is selected as a medium.

The above examples and comparative examples produce polyester resin products the coating performance results obtained according to the powder coating formulation are shown in table 1 below.

TABLE 1 results of the performance test of the powder coating coatings prepared in the examples and comparative examples

As can be seen from the comparison of examples 1-4 and comparative examples 1-2 in Table 1, the polyester resin obtained by the invention and TGIC cured coating films have the advantages of smooth appearance, excellent impact resistance, good gloss, especially excellent long-term continuous high temperature resistance, lasting high temperature resistance, no obvious change at 260 ℃/96H, high hardness of 3H or above and good adhesion through the mutual matching and synergistic effect of the components.

The organosilicon modified polyester resin adopted in the comparative example 1 has certain high temperature resistance, but the coating hardness is obviously insufficient due to the small molecular weight of the organosilicon resin, and can only reach HB;

comparative example 2 adopts the polyester resin for the conventional TGIC system, the high temperature resistance of the coating film is relatively poor, the conditions of severe yellowing and slight crack occur, and the hardness only reaches the H level, which indicates that the conventional polyester resin can not meet the application requirements of high temperature resistance and high hardness.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.