CN118813124B

CN118813124B - High-weather-resistance polyester resin powder coating and preparation method thereof

Info

Publication number: CN118813124B
Application number: CN202411078997.2A
Authority: CN
Inventors: 郑桂平; 郑利贤; 严来春
Original assignee: Jieyang Wanmei Plastic Powder Co ltd
Current assignee: Jieyang Wanmei Plastic Powder Co ltd
Priority date: 2024-08-07
Filing date: 2024-08-07
Publication date: 2024-12-10
Anticipated expiration: 2044-08-07
Also published as: CN118813124A

Abstract

The invention relates to a high weather-resistant polyester resin powder coating and a preparation method thereof, belonging to the technical field of coatings. The invention adopts self-made polyester resin, and adds 4,4' - (1-methylethylene) cyclohexanol and methyl propylene glycol in the preparation process, so that the powder coating prepared by the invention has excellent leveling property, and adds 1, 4-cyclohexanedimethanol to improve the glass transition temperature of the system, solve the problem of poor storage stability of the powder coating, and add tertiary glycidyl ester and 2-butyl-2-ethyl-1, 3-propylene glycol to exert steric hindrance effect and reduce the surface free energy of the coating, and also compound methylaminopropyl trimethoxy silane and triglycidyl isocyanurate as curing agents in the preparation process of the powder coating finished product, thereby improving the weather resistance of the prepared powder coating.

Description

High-weather-resistance polyester resin powder coating and preparation method thereof

Technical Field

The invention belongs to the technical field of coatings, and particularly relates to a high-weather-resistance polyester resin powder coating and a preparation method thereof.

Background

The powder coating is a solid powder synthetic resin coating which is composed of raw materials such as resin, curing agent, pigment, filler, auxiliary agent and the like, and gradually becomes an important raw material for coating market by virtue of the characteristics of high efficiency, energy conservation, convenience in construction and the like. With advances in technology and changes in market demand, powder coatings are widely used not only as protective coatings, but also as decorative finishes. Therefore, in this background, the powder coating is required to have excellent leveling property and storage stability, so as to prevent the powder coating from caking, layering or discoloration during storage, and prevent the defects of fish eyes, shrinkage holes, pinholes and the like of a coating film after construction due to poor leveling property of the powder coating, and meanwhile, the powder coating is required to have certain weather resistance because the powder coating is often exposed to outdoor natural environment and is often subjected to adverse conditions such as sunlight irradiation, humidity change, ozone corrosion and the like. Therefore, it is important to develop a powder coating having excellent leveling, storage stability and weather resistance.

Disclosure of Invention

The invention aims to provide a high weather-resistant polyester resin powder coating and a preparation method thereof, which solve the problems of poor leveling property, storage stability and weather resistance of the powder coating in the prior art.

The aim of the invention can be achieved by the following technical scheme:

The high weather-resistant polyester resin powder coating comprises the following raw materials in parts by weight:

As a preferable technical scheme of the invention, the curing agent comprises triglycidyl isocyanurate and methylaminopropyl trimethoxy silane, the leveling agent comprises a powder coating general-purpose leveling agent, the auxiliary agent comprises PE wax, and the pigment comprises at least one of mica iron oxide red, molybdenum chrome red, iron black, carbon black, titanium nickel yellow and cobalt green.

Further, the mass ratio of the triglycidyl isocyanurate to the methylaminopropyl trimethoxysilane is 3-4:2.5-3.

Further, the universal leveling agent for the powder coating is GLP-503.

As a preferable technical scheme of the invention, the preparation method of the self-made polyester resin specifically comprises the following steps:

Neopentyl glycol, 4' - (1-methylethylene) cyclohexanol, methyl propylene glycol, 1, 4-cyclohexanedimethanol and 2-butyl-2-ethyl-1, 3-propanediol are uniformly mixed and melted at a controlled temperature, terephthalic acid, adipic acid, tertiary glycidyl ester and monobutyl tin oxide are sequentially added after materials are clarified, nitrogen is introduced, the temperature is slowly raised and kept until no obvious distillate is distilled, the materials are subjected to primary acid value measurement, cooling, isophthalic acid end sealing is added, temperature is kept at a controlled temperature, secondary acid value measurement is performed, vacuum polycondensation is performed, tertiary acid value measurement is performed, emptying is performed, antioxidant is added at a controlled temperature, vacuum stirring and dispersing are performed, and the self-made polyester resin is obtained after discharging.

As a preferable technical scheme of the invention, 35-40 parts by weight of neopentyl glycol, 5-8 parts by weight of 4,4' - (1-methylethylene) cyclohexanol, 6-6.5 parts by weight of methyl propylene glycol, 12-18 parts by weight of 1, 4-cyclohexanedimethanol, 8-12 parts by weight of 2-butyl-2-ethyl-1, 3-propanediol, 55-65 parts by weight of terephthalic acid, 10-15 parts by weight of adipic acid, 2-3 parts by weight of versatic acid glycidyl ester, 0.08-0.1 part by weight of monobutyl tin oxide, 25-40 parts by weight of isophthalic acid and 0.5-1 part by weight of antioxidant are adopted.

As a preferred embodiment of the present invention, the antioxidant includes any one of antioxidant 1010, antioxidant 1076 and antioxidant 1098.

As a preferable technical scheme of the invention, the temperature of the temperature-controlled melting is 120-125 ℃, the temperature of the temperature rise and heat preservation is 210-220 ℃, the acid value of the primary acid value measurement is 8-12mgKOH/g, the temperature reduction is 228-230 ℃, the temperature of the temperature-controlled heat preservation is 238-240 ℃, the time is 2-3h, the acid value of the secondary acid value measurement is 43-46mgKOH/g, the acid value of the tertiary acid value measurement is 31-35mgKOH/g, the temperature of the antioxidant addition is 215-220 ℃, and the time of vacuum stirring and dispersing is 15-30min.

The preparation method of the high weather-resistant polyester resin powder coating comprises the following steps:

s1, uniformly mixing self-made polyester resin, titanium dioxide, barium sulfate, a curing agent, a leveling agent, benzoin, an auxiliary agent and pigment, and crushing to obtain a premixed material;

S2, feeding the premixed material into an extruder for temperature control extrusion, tabletting, cooling, crushing, screening and packaging to obtain a finished product of the polyester resin powder coating.

As a preferable technical scheme of the invention, the temperature of the temperature-controlled extrusion in the step S2 is 100-110 ℃, and the average particle size of the sieved powder is 30-40 mu m.

The invention has the beneficial effects that:

(1) According to the invention, 4' - (1-methylethylene) cyclohexanol and methyl propylene glycol are used as one of raw materials to participate in the synthesis of polyester resin, so that the prepared powder coating has excellent leveling property, and the overall appearance quality of the coating is ensured. Specifically, the 4,4' - (1-methylethylene) cyclohexanol symmetrically substituted by two active groups reduces the melt viscosity of the polyester resin, and the methyl propylene glycol with higher rotational freedom degree in a single bond increases the flexibility of a polyester chain segment, so that the powder coating prepared by the self-made polyester resin has excellent leveling property.

(2) According to the invention, the flexible monomer is introduced in the process of synthesizing the polyester resin, so that the storage stability of a finished product of the powder coating is easy to weaken, and therefore, on the basis of improving the problem and ensuring almost no weakening of the leveling property of the powder coating, the 1, 4-cyclohexanedimethanol with a very stable annular structure is added, so that the glass transition temperature of a system is improved, and the problem of poor storage stability of the powder coating is solved.

(3) According to the invention, the tertiary glycidyl ester with a multi-branched aliphatic structure is added in the process of synthesizing the polyester resin, and the adjacent bonds and the polyester chain segments are protected and stabilized through steric hindrance, so that the finished product has certain weather resistance, and on the basis, the 2-butyl-2-ethyl-1, 3-propanediol is further added, so that the steric hindrance effect of the polyester resin is further increased, the surface free energy of a coating is reduced, and therefore, the powder coating prepared from the polyester resin has outstanding weather resistance.

(4) On the basis, in order to consolidate the weather resistance of the powder coating, in the process of preparing a finished product of the powder coating, the methylaminopropyl trimethoxy silane and triglycidyl isocyanurate are compounded to be used as curing agents, so that a silanized polyester coating is constructed, a good network structure exists in the system, and the two synergistically strengthen the weather resistance of the powder coating.

Detailed Description

The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

The preparation method of the self-made polyester resin specifically comprises the following steps:

Uniformly mixing 40 parts by weight of neopentyl glycol, 5 parts by weight of 4,4' - (1-methylethylene) cyclohexanol, 6.5 parts by weight of methylpropanediol, 12 parts by weight of 1, 4-cyclohexanedimethanol and 10 parts by weight of 2-butyl-2-ethyl-1, 3-propanediol, controlling the temperature to be 120 ℃ for melting, sequentially adding 60 parts by weight of terephthalic acid, 10 parts by weight of adipic acid, 2.5 parts by weight of glycidyl versatate and 0.08 part by weight of monobutyl tin oxide after the materials are clarified, introducing nitrogen, slowly heating to 215 ℃ and preserving the temperature until no obvious distillate is distilled out, measuring the acid value, cooling to 229 ℃ when the acid value is 8mgKOH/g, adding 25 parts by weight of isophthalic acid for end sealing, controlling the temperature to be 238 ℃ for 2.5 hours, measuring the acid value, vacuum polycondensing when the acid value reaches 43mgKOH/g, measuring the acid value, emptying when the acid value is 31mgKOH/g, controlling the temperature to be 220 ℃ and adding 0.75 parts by weight of antioxidant 1010, carrying out vacuum stirring and dispersing for 15min, and discharging to obtain the polyester resin.

Example 2

Uniformly mixing 35 parts by weight of neopentyl glycol, 6.5 parts by weight of 4,4' - (1-methylethylene) cyclohexanol, 6 parts by weight of methylpropanediol, 15 parts by weight of 1, 4-cyclohexanedimethanol and 12 parts by weight of 2-butyl-2-ethyl-1, 3-propanediol, controlling the temperature to be 123 ℃ for melting, sequentially adding 55 parts by weight of terephthalic acid, 15 parts by weight of adipic acid, 3 parts by weight of glycidyl tertiary carbonate and 0.1 part by weight of monobutyl tin oxide after the materials are clarified, introducing nitrogen, slowly heating to 210 ℃ and preserving the temperature until no obvious distillate is distilled out, measuring the acid value, cooling to 230 ℃ when the acid value is 10mgKOH/g, adding 40 parts by weight of isophthalic acid end cap, preserving the temperature for 3h when the acid value is 240 mgKOH/g, measuring the acid value, vacuum polycondensing when the acid value reaches 46mgKOH/g, measuring the acid value, emptying when the acid value is 33mgKOH/g, controlling the temperature to 215 ℃ and adding 1 part by weight of antioxidant 1098, stirring in vacuum for 30min, and discharging to obtain the self-made polyester resin.

Example 3

37.5 parts by weight of neopentyl glycol, 8 parts by weight of 4,4' - (1-methylethylene) cyclohexanol, 6.3 parts by weight of methylpropanediol, 18 parts by weight of 1, 4-cyclohexanedimethanol and 8 parts by weight of 2-butyl-2-ethyl-1, 3-propanediol are uniformly mixed and melted at a temperature of 125 ℃, 65 parts by weight of terephthalic acid, 12.5 parts by weight of adipic acid, 2 parts by weight of glycidyl versatate and 0.09 part by weight of monobutyl tin oxide are sequentially added after the materials are clarified, nitrogen is introduced and slowly heated to 220 ℃ until no obvious distillate is distilled out, the acid value is measured, the temperature is reduced to 228 ℃ when the acid value is 12mgKOH/g, 32.5 parts by weight of isophthalic acid is blocked, the temperature is controlled to 239 ℃ for 2h, the acid value is measured, the acid value is vacuum polycondensed when the acid value reaches 44mgKOH/g, the acid value is emptied when the acid value is 35mgKOH/g, the temperature is controlled to 218 ℃ and 0.5 parts by weight of antioxidant 1076 is added, the polyester resin is vacuum stirred and dispersed for 23min, and discharged, so that the polyester resin is prepared.

Example 4

The curing agent comprises triglycidyl isocyanurate and methylaminopropyl trimethoxy silane according to the mass ratio of 3.5:2.5;

S2, feeding the premixed material into an extruder, controlling the temperature to be 100 ℃ for extrusion, tabletting, cooling, crushing, screening and packaging to obtain a polyester resin powder coating finished product;

The average particle diameter of the powder after screening in the step S2 is 30 mu m.

Example 5

The curing agent comprises triglycidyl isocyanurate and methylaminopropyl trimethoxy silane according to the mass ratio of 4:3;

s2, feeding the premixed material into an extruder, controlling the temperature to be 110 ℃ for extrusion, tabletting, cooling, crushing, screening and packaging to obtain a finished product of the polyester resin powder coating;

the average particle diameter of the powder after screening in the step S2 is 40 mu m.

Example 6

the curing agent comprises triglycidyl isocyanurate and methylaminopropyl trimethoxy silane according to the mass ratio of 3:2.8;

S2, feeding the premixed material into an extruder, controlling the temperature to be 105 ℃ for extrusion, tabletting, cooling, crushing, screening and packaging to obtain a finished product of the polyester resin powder coating;

The average particle diameter of the powder after screening in the step S2 is 35 mu m.

Comparative example 1

In comparison with example 2, the difference is that in comparative example 1, 4' - (1-methylethylene) cyclohexanol was not added, and the remaining operating steps and parameters were unchanged.

Comparative example 2

In comparison with example 2, the difference is that no methylpropanediol was added in comparative example 2, and the remaining operation steps and parameters were unchanged.

Comparative example 3

In comparison with example 2, the difference is that 1, 4-cyclohexanedimethanol was not added in comparative example 3, and the remaining operation steps and parameters were unchanged.

Comparative example 4

In comparison with example 2, the difference is that in comparative example 4, no versatic acid glycidyl ester was added, and the remaining operating steps and parameters were unchanged.

Comparative example 5

In comparison with example 2, the difference is that 2-butyl-2-ethyl-1, 3-propanediol was not added in comparative example 5, and the remaining operation steps and parameters were unchanged.

Comparative examples 6 to 10

In comparison with example 6, the difference is that in comparative examples 6 to 10, the homemade polyester resin produced in example 2 described in example 6 was replaced with the homemade polyester resin produced in comparative examples 1 to 5, respectively, and the remaining operation steps and parameters were unchanged.

Comparative example 11

In comparison with example 2, the difference is that in comparative example 11, no methylaminopropyl trimethoxysilane was added, i.e., the curing agent included triglycidyl isocyanurate, and the remaining operating steps and parameters were unchanged.

Comparative example 12

In comparison with example 2, the difference is that triglycidyl isocyanurate was not added to comparative example 12, the curing agent included methylaminopropyl trimethoxysilane, and the remaining operating steps and parameters were unchanged.

Test case

(1) Leveling property test the polyester resin powder coating finished products prepared in examples 4-6 and comparative examples 6-8 were subjected to leveling grade evaluation according to the American PCI standard flow plate, and the results are shown in Table 1;

(2) Storage stability test the polyester resin powder coating finished products prepared in examples 4 to 6 and comparative examples 6 to 8 were subjected to storage stability test according to GB/T21782.8-2008, and the results are shown in Table 1;

(3) Weather resistance test according to GSB AL 631-2017, the test conditions were adopted that a light source is a UVB-313 fluorescent ultraviolet lamp tube, the wavelength is 313nm, the irradiation intensity is 0.75W/m ², the irradiation is 4 hours at 50 ℃, the condensation is 4 hours at 40 ℃, and the weather resistance test is carried out on the polyester resin powder coating finished products prepared in examples 4-6 and comparative examples 9-12, and the results are shown in Table 2.

TABLE 1

Test item	Leveling grade/grade	Storage stability/42 ℃ x 24h
			Example 4	8	Loose and free from agglomerating
Example 5	8	Loose and free from agglomerating
			Example 6	8	Loose and free from agglomerating
Comparative example 6	5	Severe agglomeration
			Comparative example 7	5	Severe agglomeration
Comparative example 8	6	Agglomeration

As can be seen from Table 1, the powder coating prepared according to the invention has excellent leveling properties and storage stability. Because the invention uses two active groups as symmetrically substituted 4,4' - (1-methylethylene) cyclohexanol to reduce the melt viscosity of polyester resin, uses methyl propylene glycol with higher rotational freedom degree in single bond to increase the flexibility of polyester chain segment, effectively ensures the prepared powder coating to have excellent leveling property and ensures the whole appearance quality of the coating, but the flexible monomer is introduced in the process of synthesizing the polyester resin to easily lead the storage stability of the powder coating finished product to be weakened, so that the invention adds 1, 4-cyclohexanedimethanol with a very stable annular structure to improve the glass transition temperature of the system and solve the problem of poor storage stability of the powder coating, and the prepared powder coating also has excellent storage stability.

TABLE 2

Test item	Weather resistance UVB-313302h light retention (%)	Weather resistance UVB-313302h color difference
			Example 4	54.1	0.43
Example 5	53.8	0.45
			Example 6	54.5	0.40
Comparative example 9	40.9	0.97
			Comparative example 10	42.6	0.88
Comparative example 11	45.1	0.72
			Comparative example 12	46.0	0.65

As can be seen from Table 2, the powder coatings prepared according to the invention have outstanding weather resistance. The preparation method is characterized in that tertiary glycidyl ester and 2-butyl-2-ethyl-1, 3-propylene glycol are added in the process of synthesizing polyester resin to exert a steric hindrance effect and reduce the surface free energy of a coating, and methylaminopropyl trimethoxy silane and triglycidyl isocyanurate are compounded to serve as a curing agent in the process of preparing a finished product of the powder coating, so that a good network structure exists in a system, and therefore, the prepared powder coating has outstanding weather resistance.

In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing is merely illustrative and explanatory of the invention, as various modifications and additions may be made to the particular embodiments described, or in a similar manner, by those skilled in the art, without departing from the scope of the invention or exceeding the scope of the invention as defined in the claims.

Claims

1. A highly weather-resistant polyester resin powder coating, characterized in that it specifically comprises the following raw materials in parts by weight:

Homemade polyester resin 80-90 parts by weight

Titanium dioxide 28-30 parts by weight

Barium sulfate 25-28 parts by weight

Curing agent 8-10 parts by weight

Leveling agent 3-5 parts by weight

Benzoin 0.8-1 weight part

Auxiliary agent 0.4-0.6 weight part

Pigment 3-6 parts by weight;

Neopentyl glycol, 4,4'-(1-methylethylidene)dicyclohexanol, methyl propanediol, 1,4-cyclohexanedimethanol and 2-butyl-2-ethyl-1,3-propanediol are uniformly mixed and melted under controlled temperature, terephthalic acid, adipic acid, tert-carbonic acid glycidyl ester and monobutyltin oxide are added in sequence after the material is clarified, nitrogen is passed and the temperature is slowly increased and kept warm until no obvious distillate is evaporated, the acid value is measured once, the temperature is increased, isophthalic acid is added for end-capping, the temperature is controlled and kept warm again, the acid value is measured twice, vacuum polycondensation is carried out, the acid value is measured three times, the material is vented, the temperature is controlled again, an antioxidant is added, vacuum stirring and dispersion is carried out, and the material is discharged to obtain a self-made polyester resin;

Wherein, the neopentyl glycol is 35-40 parts by weight, the 4,4'-(1-methylethylidene)bicyclohexanol is 5-8 parts by weight, the methyl propanediol is 6-6.5 parts by weight, the 1,4-cyclohexanedimethanol is 12-18 parts by weight, the 2-butyl-2-ethyl-1,3-propanediol is 8-12 parts by weight, the terephthalic acid is 55-65 parts by weight, the adipic acid is 10-15 parts by weight, the versatile glycidyl carbonate is 2-3 parts by weight, the monobutyl tin oxide is 0.08-0.1 parts by weight, the isophthalic acid is 25-40 parts by weight, and the antioxidant is 0.5-1 parts by weight;

The curing agent includes triglycidyl isocyanurate and methylaminopropyl trimethoxysilane; and the auxiliary agent is PE wax.

2. The highly weather-resistant polyester resin powder coating according to claim 1 is characterized in that the leveling agent includes a universal leveling agent for powder coatings; and the pigment includes at least one of mica iron oxide red, molybdenum chrome red, iron black, carbon black, titanium nickel yellow and cobalt green.

3. The highly weather-resistant polyester resin powder coating according to claim 1, characterized in that the mass ratio of triglycidyl isocyanurate to methylaminopropyltrimethoxysilane is 3-4:2.5-3.

4. The highly weather-resistant polyester resin powder coating according to claim 2, characterized in that the universal leveling agent for powder coating is GLP-503.

5 . The highly weather-resistant polyester resin powder coating according to claim 1 , characterized in that the antioxidant comprises any one of antioxidant 1010, antioxidant 1076 and antioxidant 1098.

6. The highly weather-resistant polyester resin powder coating according to claim 5 is characterized in that the temperature of the temperature-controlled melting is 120-125°C; the temperature of the heating and insulation is 210-220°C; the acid value of the first acid measurement is 8-12 mgKOH/g; the heating is to 228-230°C; the temperature of the temperature-controlled insulation is 238-240°C, and the time is 2-3h; the acid value of the second acid measurement is 43-46 mgKOH/g; the acid value of the third acid measurement is 31-35 mgKOH/g; the temperature of the temperature-controlled addition of the antioxidant is 215-220°C; and the time of the vacuum stirring and dispersing is 15-30min.

7. A method for preparing the highly weather-resistant polyester resin powder coating according to any one of claims 1 to 6, characterized in that the preparation method specifically comprises the following steps:

S1, mixing and crushing the homemade polyester resin, titanium dioxide, barium sulfate, curing agent, leveling agent, benzoin, additives and pigment to obtain a premixed material;

S2. The premixed material is fed into an extruder for temperature-controlled extrusion, and is tableted, cooled, crushed, sieved, and packaged to obtain a finished polyester resin powder coating.

8. The method for preparing a highly weather-resistant polyester resin powder coating according to claim 7, characterized in that the temperature of the temperature-controlled extrusion in step S2 is 100-110°C; and the average particle size of the powder after screening is 30-40 μm.