阅读说明：本技术 一种耐水性优的粉末涂料用聚酯树脂及其制备方法 (Polyester resin with excellent water resistance for powder coating and preparation method thereof ) 是由 毕海鹏 江蓉 郑荣辉 张齐 冯小浩 于 2021-09-30 设计创作，主要内容包括：提供了一种耐水优的粉末用聚酯树脂及其制备方法,其采用己二酸二甲酯、1,8-萘二甲酸酐、四甲基乙二醇,利用酯交换的方式制备出功能性的疏水中间体聚合物,然后再与十二羟基硬脂酸、对苯二甲酸、新戊二醇、间苯二甲酸进行聚合反应得到。由于在聚酯树脂链段中引入支链疏水能力强的基团,当将该聚酯树脂用于TGIC固化体系中时,最终固化涂膜综合性能较佳,耐候性出色,成本相对较低,尤其是长时间的耐高压沸水煮性能优异,适合用于户外长期接触水的环境中使用。(The polyester resin is prepared by preparing a functional hydrophobic intermediate polymer by adopting dimethyl adipate, 1, 8-naphthalic anhydride and tetramethylethylene glycol in an ester exchange mode and then carrying out polymerization reaction on the intermediate polymer, dodecahydroxystearic acid, terephthalic acid, neopentyl glycol and isophthalic acid. Because a group with strong branched chain hydrophobic ability is introduced into a polyester resin chain segment, when the polyester resin is used in a TGIC curing system, the final cured coating film has good comprehensive performance, excellent weather resistance and relatively low cost, particularly has excellent high-pressure boiling water boiling resistance for a long time, and is suitable for being used in an outdoor environment contacting water for a long time.)

1. The polyester resin for the powder coating has excellent water resistance, and consists of the following raw materials in molar parts:

wherein, a catalyst is also added in the preparation process of the polyester resin, the catalyst is dibutyltin oxide, and the dosage of the catalyst is 0.05-0.1 percent of the total molar weight of the raw materials.

2. The polyester resin for powder coating according to claim 1, wherein the polyester resin has an acid value of 30 to 36mgKOH/g and a softening point of 115-125 ℃.

3. The method for preparing the polyester resin for powder coating according to claims 1-2, comprising:

(1) adding 6-10 parts by mole of dimethyl adipate and 18-30 parts by mole of tetramethyl glycol into a reaction kettle, heating to 110-;

(2) adding 13-22 molar parts of 1, 8-naphthalic anhydride and 0.05-0.1% of catalyst by total molar weight of raw materials into the first mixture obtained in the step (1), and fully reacting at 110-115 ℃;

(3) when the hydroxyl value of the reactants of the system reaches 23-30mgKOH/g, starting vacuum to carry out deep ester exchange reaction;

(4) when the hydroxyl value of the reactants of the system is lower than 5mgKOH/g, releasing the vacuum, adding 10-17 molar parts of dodecahydroxystearic acid, 7-14 molar parts of terephthalic acid and 10-20 molar parts of neopentyl glycol, heating to 240 ℃, and preserving the temperature for reaction;

(5) when the acid value of the system reactant reaches 45-50mgKOH/g, the vacuum system is started again to carry out vacuum polycondensation;

(6) when the acid value of the system reactant is reduced to 15-18mgKOH/g, releasing the vacuum, and adding 5-9 molar parts of isophthalic acid for end-capping reaction;

(7) and stopping the reaction when the acid value of the reactants of the system reaches 30-36mgKOH/g, discharging, cooling, and crushing and granulating to obtain the polyester resin.

4. The method of preparing polyester resin for powder coating according to claim 3, wherein in the step (3), the degree of vacuum is controlled to be-0.095 to-0.097 MPa.

5. The method for preparing a polyester resin for powder coating according to claim 3, wherein the temperature is raised at a temperature-raising rate of 7 to 9 ℃/h in the step (4).

6. The method of preparing polyester resin for powder coating according to claim 3, wherein in the step (5), the degree of vacuum is controlled to be-0.095 to-0.097 MPa.

7. The method for preparing polyester resin for powder coating according to claim 3, wherein said discharging in step (7) is discharging while hot at a high temperature, and said cooling is cooling with a steel belt with condensed water.

8. A powder coating material comprising the polyester resin for powder coating material according to claim 1 or 2.

9. A powder coating prepared from the powder coating of claim 8.

Technical Field

The invention relates to the field of powder coatings, in particular to polyester resin for a powder coating with excellent water resistance and a preparation method thereof.

Background

At present, a lot of metal facilities (such as guardrails, floors and the like) beside lakes and outdoor swimming pools are easy to rust due to long-time water contact, and after a coating film is coated by a common powder coating, the defects of cracking, falling and the like of the coating film are caused due to the insufficient long-term water resistance and outdoor weather resistance, so that the application of the coating film in related fields is seriously influenced.

At present, special polyester resin varieties (such as Chinese patent applications CN110804164A, CN110117355A and the like) adopt special fluorine elements with strong hydrophobicity, so that the comprehensive performance is good, but the cost is extremely high. However, the Chinese patent application CN202010643664.5 not only needs to use fluorine element, but also needs to use the special prepared poly-phenol-oxygen resin, so the preparation process is complicated, the cost is extremely high, and the method is not suitable for coating common powder coating.

Therefore, it is highly desirable to develop a polyester resin for powder coating with excellent water resistance and a method for preparing the same to solve the above-mentioned problems.

Disclosure of Invention

Therefore, the invention provides a polyester resin for powder coating with excellent water resistance, which consists of the following raw materials in molar parts:

wherein, a catalyst is also added in the preparation process of the polyester resin, the catalyst is dibutyltin oxide, and the dosage of the catalyst is 0.05-0.1 percent of the total molar weight of the raw materials.

Wherein the polyester resin is colorless transparent particles, the acid value is 30-36mgKOH/g, and the softening point is 115-125 ℃.

The invention also provides a preparation method of the polyester resin for the powder coating, which comprises the following steps:

(1) adding 6-10 parts by mole of dimethyl adipate and 18-30 parts by mole of tetramethyl glycol into a reaction kettle, heating to 110-;

(2) adding 13-22 molar parts of 1, 8-naphthalic anhydride and 0.05-0.1% of catalyst by total molar weight of raw materials into the first mixture obtained in the step (1), and fully reacting at 110-115 ℃;

(3) when the hydroxyl value of the reactants of the system reaches 23-30mgKOH/g, starting vacuum to carry out deep ester exchange reaction;

(4) when the hydroxyl value of the reactants of the system is lower than 5mgKOH/g, releasing the vacuum, adding 10-17 molar parts of dodecahydroxystearic acid, 7-14 molar parts of terephthalic acid and 10-20 molar parts of neopentyl glycol, heating to 240 ℃, and preserving the temperature for reaction;

(5) when the acid value of the system reactant reaches 45-50mgKOH/g, the vacuum system is started again to carry out vacuum polycondensation;

(6) when the acid value of the system reactant is reduced to 15-18mgKOH/g, releasing the vacuum, and adding 5-9 molar parts of isophthalic acid for end-capping reaction;

(7) and stopping the reaction when the acid value of the reactants of the system reaches 30-36mgKOH/g, discharging, cooling, and crushing and granulating to obtain the polyester resin.

Wherein, in the step (3), the vacuum degree is controlled to be-0.095 to-0.097 Mpa.

Wherein, in the step (4), the temperature is increased at a temperature increasing speed of 7-9 ℃/h.

Wherein in the step (5), the vacuum degree is controlled to be-0.095 to-0.097 MPa.

In the step (7), the discharging is discharging at a high temperature while the discharging is hot, and the cooling is performed by using a steel strip with condensed water.

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

The invention also provides a powder coating prepared from the powder coating.

The invention has the following beneficial technical effects:

1. the invention adopts dimethyl adipate, 1, 8-naphthalic anhydride and tetramethylglycol to prepare a functional hydrophobic intermediate polymer by an ester exchange mode, and then the functional hydrophobic intermediate polymer is polymerized with dodecahydroxystearic acid, terephthalic acid, neopentyl glycol and isophthalic acid to obtain the polyester resin for powder coating.

2. Because the polyester resin chain segment of the invention is introduced with groups with strong branched chain hydrophobic ability (such as tertiary butyl of tetramethyl glycol, alkyl of long-chain eleven carbon of dodecahydroxy stearic acid, naphthyl and the like), when the polyester resin for powder coating is used in a TGIC curing system, the final cured coating film has good comprehensive performance, excellent weather resistance and relatively low cost, particularly has excellent high-pressure boiling resistance for a long time, and is suitable for being used in an outdoor environment contacting water for a long time. The surface of the coating prepared by the product of the invention basically has no obvious change after the coating is boiled in high pressure water for 12 hours, the dry adhesion is still at 0 level, and the surface of the coating has no change after 120 days of continuous water-resistant soaking, which shows that the product of the invention has excellent water resistance. In addition, the invention does not use expensive fluorine-silicon hydrophobic elements, has relatively low cost and is easy to popularize and apply on a large scale.

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 method for preparing polyester resin for powder coating with excellent water resistance comprises the following steps:

(1) adding 7 molar parts of dimethyl adipate and 20 molar parts of tetramethylethylene glycol into a reaction kettle, heating to 111 ℃, and stirring to be fully melted to obtain a first mixture;

(2) adding 14 molar parts of 1, 8-naphthalic anhydride and 0.06% of catalyst in terms of total molar amount of raw materials into the first mixture obtained in the step (1), and fully reacting at 111 ℃;

(3) when the hydroxyl value of the reactants of the system reaches 24mgKOH/g, starting vacuum, controlling the vacuum degree to be-0.096 Mpa, and carrying out deep ester exchange reaction;

(4) when the hydroxyl value of the reactants of the system is lower than 5mgKOH/g, releasing the vacuum, adding 11 mol parts of dodecahydroxystearic acid, 8 mol parts of terephthalic acid and 12 mol parts of neopentyl glycol, heating to 236 ℃ at the heating rate of 7 ℃/h, and preserving the heat for reaction;

(5) when the acid value of the system reactant reaches 46mgKOH/g, the vacuum system is started again, the vacuum degree is controlled at-0.0956 Mpa, the vacuum polycondensation reaction is carried out,

(6) when the acid value of the system reactant is reduced to 16mgKOH/g, the vacuum is relieved, and 6 molar parts of isophthalic acid are added for end capping reaction;

(7) and stopping the reaction when the acid value of the system reactant reaches 32mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.

The polyester resin was colorless transparent particles in appearance, and had an acid value of 32mgKOH/g and a softening point of 119 ℃.

Example 2

A method for preparing polyester resin for powder coating with excellent water resistance comprises the following steps:

(1) adding 9 molar parts of dimethyl adipate and 28 molar parts of tetramethylethylene glycol into a reaction kettle, heating to 114 ℃, and stirring for full melting to obtain a first mixture;

(2) adding 21 molar parts of 1, 8-naphthalic anhydride and 0.09% of catalyst which is used for the total molar amount of raw materials into the first mixture obtained in the step (1), and fully reacting at 114 ℃;

(3) when the hydroxyl value of the reactants of the system reaches 28mgKOH/g, starting vacuum, controlling the vacuum degree to be-0.095 Mpa, and carrying out deep ester exchange reaction;

(4) when the hydroxyl value of the reactants of the system is lower than 5mgKOH/g, releasing the vacuum, adding 16 mol parts of dodecahydroxystearic acid, 13 mol parts of terephthalic acid and 18 mol parts of neopentyl glycol, heating to 238 ℃ at the heating rate of 9 ℃/h, and preserving the heat for reaction;

(5) when the acid value of the system reactant reaches 49mgKOH/g, the vacuum system is started again, the vacuum degree is controlled at-0.095 Mpa, the vacuum polycondensation reaction is carried out,

(6) when the acid value of the system reactant is reduced to 17mgKOH/g, releasing the vacuum, and adding 8 molar parts of isophthalic acid to carry out end-capping reaction;

(7) and stopping the reaction when the acid value of the system reactant reaches 35mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.

The polyester resin was colorless transparent particles in appearance, and had an acid value of 35mgKOH/g and a softening point of 123 ℃.

Example 3

A method for preparing polyester resin for powder coating with excellent water resistance comprises the following steps:

(1) adding 6 molar parts of dimethyl adipate and 24 molar parts of tetramethylethylene glycol into a reaction kettle, heating to 113 ℃, and stirring for full melting to obtain a first mixture;

(2) adding 17 molar parts of 1, 8-naphthalic anhydride and 0.07 percent of catalyst which is used for the total molar amount of raw materials into the first mixture obtained in the step (1), and fully reacting at 113 ℃;

(3) when the hydroxyl value of the reactants of the system reaches 26mgKOH/g, starting vacuum, controlling the vacuum degree to be-0.097 Mpa, and carrying out deep ester exchange reaction;

(4) when the hydroxyl value of the reactants of the system is lower than 5mgKOH/g, releasing the vacuum, adding 14 molar parts of dodecahydroxystearic acid, 11 molar parts of terephthalic acid and 15 molar parts of neopentyl glycol, heating to 237 ℃ at the heating rate of 8 ℃/h, and preserving the heat for reaction;

(5) when the acid value of the system reactant reaches 47mgKOH/g, the vacuum system is started again, the vacuum degree is controlled at-0.097 Mpa, the vacuum polycondensation reaction is carried out,

(6) when the acid value of the system reactant is reduced to 17mgKOH/g, releasing the vacuum, and adding 7 molar parts of isophthalic acid for end capping reaction;

(7) and stopping the reaction when the acid value of the system reactant reaches 33mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.

The polyester resin was colorless transparent particles in appearance, and had an acid value of 33mgKOH/g and a softening point of 120 ℃.

Example 4

A method for preparing polyester resin for powder coating with excellent water resistance comprises the following steps:

(1) adding 6 molar parts of dimethyl adipate and 30 molar parts of tetramethylethylene glycol into a reaction kettle, heating to 115 ℃, and stirring for full melting to obtain a first mixture;

(2) adding 22 molar parts of 1, 8-naphthalic anhydride and 0.1 percent of catalyst which is used for the total molar amount of raw materials into the first mixture obtained in the step (1), and fully reacting at 115 ℃;

(3) when the hydroxyl value of the reactants of the system reaches 25mgKOH/g, starting vacuum, controlling the vacuum degree to be-0.095 Mpa, and carrying out deep ester exchange reaction;

(4) when the hydroxyl value of the reactants of the system is lower than 5mgKOH/g, releasing the vacuum, adding 10 molar parts of dodecahydroxystearic acid, 14 molar parts of terephthalic acid and 10 molar parts of neopentyl glycol, heating to 235 ℃ at the heating rate of 9 ℃/h, and preserving the heat for reaction;

(5) when the acid value of the system reactant reaches 50mgKOH/g, the vacuum system is started again, the vacuum degree is controlled at-0.095 Mpa, the vacuum polycondensation reaction is carried out,

(6) when the acid value of the system reactant is reduced to 18mgKOH/g, the vacuum is relieved, and 5 molar parts of isophthalic acid are added for end capping reaction;

(7) and stopping the reaction when the acid value of the reactants of the system reaches 36mgKOH/g, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the polyester resin.

The polyester resin was colorless transparent particles in appearance, and had an acid value of 36mgKOH/g and a softening point of 125 ℃.

Comparative example 1

A polyester resin for powder coating of a commercially available ordinary TGIC system, which was purchased from new material of ansu sword, inc, model number SJ4E, was used as comparative example 1; the acid value of the polyester resin was 31mgKOH/g, and the softening point was 115 ℃.

Preparation of TGIC powder coatings:

the TGIC powder coatings of examples 1-4 and comparative example 1 were prepared using the polyester resins of examples 1-4 and comparative example 1, respectively, according to the following powder coating formulation, wherein the component contents are in parts by weight:

preparation of TGIC powder paint coatings:

the TGIC powder coatings of examples 1-4 and comparative example 1 were prepared by blending the materials, extruding with a twin screw extruder, tabletting, crushing, pulverizing and sieving the flakes, respectively, according to the formulation of TGIC powder coatings of examples 1-4 and comparative example 1. Then, the powder coatings of the examples 1 to 4 and the comparative example 1 are respectively sprayed on the galvanized iron plate after surface treatment by an electrostatic spray gun and cured at 200 ℃/10min to obtain the powder coating coatings of the examples 1 to 4 and the comparative example 1.

And (3) testing the performance of the coating:

and (3) detection of coating indexes: according to GB/T21776 & 2008 & ltStandard guidelines for testing powder coatings and coatings thereof';

detecting the high-pressure resistant boiling performance: according to section 6.13 of GB/T8013.3-2018;

and (3) continuous water-resistant soaking performance test: soaking the sample plate in bottled water, sealing the sample plate, standing at room temperature, and observing the change of a coating film;

and (3) testing weather resistance: according to cycle A mode in GB/T1865-2009 Artificial weathering and Artificial radiation Exposure of paints and varnishes.

The results of the coating property tests are shown in table 1.

TABLE 1 test results of coating properties of powder coatings of examples and comparative examples

As can be seen from Table 1, the coating films prepared in examples 1 to 4 of the present invention exhibited excellent properties in appearance, impact resistance, gloss, resistance to high-pressure boiling, continuous water-soaking resistance, and weather resistance. Particularly, in the aspect of water resistance, the surfaces of the coatings prepared according to the examples 1 to 4 of the invention have no obvious change basically after being boiled in high-pressure water for 12 hours, the dry adhesion is still at the level of 0, and the surfaces of the coatings have no change after being continuously soaked in water for 120 days, which shows that the water resistance of the products of the invention is very excellent. In addition, the invention does not use expensive fluorine-silicon hydrophobic elements, has relatively low cost and is easy to popularize and apply on a large scale.

The coating prepared using the commercially available common TGIC system polyester resin of comparative example 1 exhibited severe loss of gloss on the surface after long-term high-pressure boiling and slight bubbling after 120 days of water immersion, which indicates insufficient water resistance in the coating and was not suitable for use in an environment where water was in contact for a long period of time.

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.