A kind of highly weather-resistant polyester resin powder coating and preparation method thereof

Abstract

The present invention relates to a highly weather-resistant polyester resin powder coating and a preparation method thereof, and belongs to the technical field of coatings, and includes the following raw materials: homemade polyester resin, titanium dioxide, barium sulfate, curing agent, leveling agent, benzoin, auxiliary agent and pigment. The present invention adopts homemade polyester resin and adds 4,4'-(1-methylethylidene) dicyclohexanol and methyl propylene glycol to obtain powder coating with excellent leveling performance during its preparation process; 1,4-cyclohexanedimethanol is added to improve the glass transition temperature of the system, and the problem of poor storage stability of powder coating is solved; tertiary carbonic acid glycidyl ester and 2-butyl-2-ethyl-1,3-propylene glycol are added to exert steric hindrance effect and reduce the surface free energy of coating, together with methylaminopropyl trimethoxysilane and triglycidyl isocyanurate compounded as curing agent in the process of preparing powder coating finished product, the weather resistance of obtained powder coating is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a highly weather-resistant polyester resin powder coating and a preparation method thereof. Background Art

[0002] Powder coating is a solid powdered synthetic resin coating composed of raw materials such as resin, curing agent, pigment, filler and additive. It has gradually become an important raw material used in the coating market due to its high efficiency, energy saving and easy construction. With the advancement of science and technology and the changes in market demand, powder coating is not only used as a protective coating, but also widely used in decorative finishes. Therefore, under this background, powder coating is required to have excellent leveling and storage stability to prevent the powder coating from agglomerating, stratifying or discoloring during storage, and to prevent the coating film from having defects such as fish eyes, shrinkage holes and pinholes due to poor leveling of powder coating after construction; at the same time, since powder coating is often exposed to the outdoor natural environment, it is often affected by adverse conditions such as sunlight, humidity changes, and ozone erosion, so it needs to have certain weather resistance. Therefore, it is particularly important to develop a powder coating with excellent leveling, storage stability and weather resistance. Summary of the invention

[0003] The purpose of the present invention is to provide a highly weather-resistant polyester resin powder coating and a preparation method thereof, which solves the problems of poor leveling, storage stability and weather resistance of the powder coating in the prior art.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A highly weather-resistant polyester resin powder coating, specifically comprising the following raw materials in parts by weight:

[0006]

[0007]

[0008] As a preferred technical solution of the present invention, the curing agent includes triglycidyl isocyanurate and methylaminopropyl trimethoxysilane; the leveling agent includes a universal leveling agent for powder coatings; the auxiliary agent includes PE wax; the pigment includes but is not limited to at least one of mica iron oxide red, molybdenum chrome red, iron black, carbon black, titanium nickel yellow and cobalt green.

[0009] Furthermore, the mass ratio of triglycidyl isocyanurate to methylaminopropyltrimethoxysilane is 3-4:2.5-3.

[0010] Furthermore, the universal leveling agent for powder coatings is GLP-503.

[0011] As a preferred technical solution of the present invention, the method for preparing the homemade polyester resin specifically comprises the following steps:

[0012] 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. After the material is clarified, terephthalic acid, adipic acid, tert-butyl glycidyl carbonate and monobutyl tin oxide are added in sequence. Nitrogen is passed through and the temperature is slowly increased and kept warm until no obvious distillate is evaporated. The acid value is measured once, the temperature is lowered, 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, an antioxidant is added, vacuum stirring and dispersion is carried out, and the material is discharged to obtain a self-made polyester resin.

[0013] As a preferred technical solution of the present invention, 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.

[0014] As a preferred technical solution of the present invention, the antioxidant includes any one of antioxidant 1010, antioxidant 1076 and antioxidant 1098.

[0015] As a preferred technical solution of the present invention, 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 cooling is to cool 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 dispersion is 15-30min.

[0016] A method for preparing a highly weather-resistant polyester resin powder coating, the preparation method specifically comprising the following steps:

[0017] 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;

[0018] 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.

[0019] As a preferred technical solution of the present invention, 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.

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention uses 4,4'-(1-methylethylidene)dicyclohexanol and methylpropanediol as one of the raw materials to participate in the synthesis of polyester resin, which can effectively make the prepared powder coating have excellent leveling performance and ensure the overall appearance quality of the coating. Specifically, 4,4'-(1-methylethylidene)dicyclohexanol with two active groups symmetrically substituted reduces the melt viscosity of the polyester resin; methylpropanediol with a high degree of rotation freedom within the single bond increases the flexibility of the polyester chain segment; therefore, the powder coating prepared by the self-made polyester resin of the present invention has excellent leveling performance.

[0022] (2) The present invention introduces a flexible monomer during the synthesis of the polyester resin, which can easily lead to a weakening of the storage stability of the finished powder coating. Therefore, in order to improve this problem while ensuring that the leveling property of the powder coating is almost not weakened, the present invention adds 1,4-cyclohexanedimethanol with a very stable cyclic structure to increase the glass transition temperature of the system, thereby solving the problem of poor storage stability of the powder coating.

[0023] (3) In the process of synthesizing the polyester resin, the present invention adds tert-butyl glycidyl carbonate having a multi-branched aliphatic structure, which protects and stabilizes adjacent bonds and the polyester chain segments themselves through steric hindrance, thereby making the finished product have certain weather resistance. On this basis, 2-butyl-2-ethyl-1,3-propanediol is added to further increase the steric hindrance effect of the polyester resin and reduce the surface free energy of the coating. Therefore, the powder coating prepared using the polyester resin of the present invention has outstanding weather resistance.

[0024] (4) On the basis of the above, in order to enhance the weather resistance of the powder coating, the present invention compounded methylaminopropyl trimethoxysilane and triglycidyl isocyanurate as curing agents in the process of preparing the finished powder coating to construct a silanized polyester coating, so that a good network structure exists in the system. The two synergistically enhance the weather resistance of the powder coating. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] A self-made polyester resin, wherein the preparation method of the self-made polyester resin specifically comprises the following steps:

[0028] 40 parts by weight of neopentyl glycol, 5 parts by weight of 4,4'-(1-methylethylidene)dicyclohexanol, 6.5 parts by weight of methyl propanediol, 12 parts by weight of 1,4-cyclohexanedimethanol and 10 parts by weight of 2-butyl-2-ethyl-1,3-propanediol were mixed uniformly and melted at 120°C. After the material was clarified, 60 parts by weight of terephthalic acid, 10 parts by weight of adipic acid, 2.5 parts by weight of tert-butyl carbonate glycidyl ester and 0.08 parts by weight of monobutyl tin oxide were added in sequence, and nitrogen was passed through and the temperature was slowly raised. To 215 ° C and keep warm until no obvious distillate is evaporated, measure the acid value, when the acid value is 8 mgKOH / g, reduce the temperature to 229 ° C, add 25 parts by weight of isophthalic acid to seal, then control the temperature to 238 ° C and keep warm for 2.5 hours, measure the acid value, when the acid value reaches 43 mgKOH / g, vacuum polycondense, measure the acid value, when the acid value is 31 mgKOH / g, vent, control the temperature to 220 ° C, add 0.75 parts by weight of antioxidant 1010, stir and disperse in a vacuum for 15 minutes, discharge the material, and obtain the homemade polyester resin.

[0029] Example 2

[0030] A self-made polyester resin, wherein the preparation method of the self-made polyester resin specifically comprises the following steps:

[0031] 35 parts by weight of neopentyl glycol, 6.5 parts by weight of 4,4'-(1-methylethylidene)dicyclohexanol, 6 parts by weight of methylpropylene glycol, 15 parts by weight of 1,4-cyclohexanedimethanol and 12 parts by weight of 2-butyl-2-ethyl-1,3-propanediol were mixed uniformly and melted at 123°C. After the material was clarified, 55 parts by weight of terephthalic acid, 15 parts by weight of adipic acid, 3 parts by weight of tert-butyl carbonate glycidyl ester and 0.1 parts by weight of monobutyltin oxide were added in sequence, and nitrogen was passed through and the temperature was slowly raised. To 210℃ and keep warm until no obvious distillate is evaporated, measure the acid value, when the acid value is 10mgKOH / g, reduce the temperature to 230℃, add 40 parts by weight of isophthalic acid to seal, then control the temperature to 240℃ and keep warm for 3h, measure the acid value, when the acid value reaches 46mgKOH / g, carry out vacuum condensation, measure the acid value, when the acid value is 33mgKOH / g, vent, control the temperature to 215℃, add 1 part by weight of antioxidant 1098, stir and disperse in vacuum for 30min, discharge the material, and obtain the homemade polyester resin.

[0032] Example 3

[0033] A self-made polyester resin, wherein the preparation method of the self-made polyester resin specifically comprises the following steps:

[0034] 37.5 parts by weight of neopentyl glycol, 8 parts by weight of 4,4'-(1-methylethylidene)dicyclohexanol, 6.3 parts by weight of methyl propanediol, 18 parts by weight of 1,4-cyclohexanedimethanol and 8 parts by weight of 2-butyl-2-ethyl-1,3-propanediol were mixed uniformly and melted at 125°C. After the material was clarified, 65 parts by weight of terephthalic acid, 12.5 parts by weight of adipic acid, 2 parts by weight of tert-butyl carbonate glycidyl ester and 0.09 parts by weight of monobutyl tin oxide were added in sequence, and nitrogen was passed through and the temperature was slowly raised. To 220℃ and keep warm until no obvious distillate is evaporated, measure the acid value, when the acid value is 12 mgKOH / g, reduce the temperature to 228℃, add 32.5 parts by weight of isophthalic acid to seal, then control the temperature to 239℃ and keep warm for 2h, measure the acid value, when the acid value reaches 44mgKOH / g, carry out vacuum condensation, measure the acid value, when the acid value is 35mgKOH / g, vent, control the temperature to 218℃, add 0.5 parts by weight of antioxidant 1076, stir and disperse in vacuum for 23min, discharge the material, and obtain the homemade polyester resin.

[0035] Example 4

[0036] A highly weather-resistant polyester resin powder coating, specifically comprising the following raw materials in parts by weight:

[0037]

[0038] The curing agent comprises triglycidyl isocyanurate and methylaminopropyl trimethoxysilane in a mass ratio of 3.5:2.5;

[0039] 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;

[0040] S2, feeding the premixed material into an extruder and extruding it at a controlled temperature of 100° C., tableting, cooling, crushing, screening, and packaging to obtain a finished polyester resin powder coating;

[0041] The average particle size of the powder after sieving in step S2 is 30 μm.

[0042] Example 5

[0043] A highly weather-resistant polyester resin powder coating, specifically comprising the following raw materials in parts by weight:

[0044]

[0045]

[0046] The curing agent comprises triglycidyl isocyanurate and methylaminopropyl trimethoxysilane in a mass ratio of 4:3;

[0047] 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;

[0048] S2, feeding the premixed material into an extruder and extruding it at a controlled temperature of 110° C., tableting, cooling, crushing, screening, and packaging to obtain a finished polyester resin powder coating;

[0049] The average particle size of the powder after sieving in step S2 is 40 μm.

[0050] Example 6

[0051] A highly weather-resistant polyester resin powder coating, specifically comprising the following raw materials in parts by weight:

[0052]

[0053] The curing agent comprises triglycidyl isocyanurate and methylaminopropyl trimethoxysilane in a mass ratio of 3:2.8;

[0054] 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;

[0055] S2, feeding the premixed material into an extruder and extruding it at a controlled temperature of 105°C, tableting, cooling, crushing, screening, and packaging to obtain a finished polyester resin powder coating;

[0056] The average particle size of the powder after sieving in step S2 is 35 μm.

[0057] Comparative Example 1

[0058] Compared with Example 2, the difference is that in Comparative Example 1, 4,4'-(1-methylethylidene)bicyclohexanol is not added, and the other operating steps and parameters remain unchanged.

[0059] Comparative Example 2

[0060] Compared with Example 2, the difference is that methyl propanediol is not added in Comparative Example 2, and the other operating steps and parameters remain unchanged.

[0061] Comparative Example 3

[0062] Compared with Example 2, the difference is that in Comparative Example 3, 1,4-cyclohexanedimethanol is not added, and the other operating steps and parameters remain unchanged.

[0063] Comparative Example 4

[0064] Compared with Example 2, the difference is that no tert-butyl glycidyl carbonate is added in Comparative Example 4, and the other operating steps and parameters remain unchanged.

[0065] Comparative Example 5

[0066] Compared with Example 2, the difference is that in Comparative Example 5, 2-butyl-2-ethyl-1,3-propanediol is not added, and the other operating steps and parameters remain unchanged.

[0067] Comparative Examples 6-10

[0068] Compared with Example 6, the difference is that in Comparative Examples 6-10, the homemade polyester resin prepared in Example 2 of Example 6 is replaced by the homemade polyester resin prepared in Comparative Examples 1-5, respectively, and the other operating steps and parameters remain unchanged.

[0069] Comparative Example 11

[0070] Compared with Example 2, the difference is that in Comparative Example 11, methylaminopropyltrimethoxysilane is not added, that is, the curing agent includes triglycidyl isocyanurate, and the other operating steps and parameters remain unchanged.

[0071] Comparative Example 12

[0072] Compared with Example 2, the difference is that in Comparative Example 12, triglycidyl isocyanurate is not added, the curing agent includes methylaminopropyltrimethoxysilane, and the other operating steps and parameters remain unchanged.

[0073] Test Case

[0074] (1) Leveling performance test: The leveling grade of the finished polyester resin powder coatings prepared in Examples 4-6 and Comparative Examples 6-8 was evaluated according to the U.S. PCI standard leveling plate. The results are shown in Table 1.

[0075] (2) Storage stability test: According to GB / T 21782.8-2008, the polyester resin powder coating products prepared in Examples 4-6 and Comparative Examples 6-8 were subjected to storage stability tests. The results are shown in Table 1.

[0076] (3) Weathering resistance test: According to GSB AL 631-2017, the test conditions are: Light source: UVB-313 fluorescent ultraviolet lamp, wavelength 313nm, irradiation intensity 0.75W / m 2 , 50℃ light exposure for 4h, 40℃ condensation for 4h; the polyester resin powder coating products prepared in Examples 4-6 and Comparative Examples 9-12 were tested for weather resistance, and the results are shown in Table 2.

[0077] Table 1

[0078] Test items Leveling grade / level Storage stability / 42℃×24h Example 4 8 Loose and non-clustered Example 5 8 Loose and non-clustered Example 6 8 Loose and non-clustered Comparative Example 6 5 Severe clumping Comparative Example 7 5 Severe clumping Comparative Example 8 6 Clustering

[0079] As can be seen from Table 1, the powder coating prepared by the present invention has excellent leveling performance and storage stability. This is because the present invention uses 4,4'-(1-methylethylidene)dicyclohexanol with two active groups as symmetrical substitution to reduce the melt viscosity of the polyester resin, and uses methylpropanediol with a high degree of rotation freedom within the single bond to increase the flexibility of the polyester segment, which effectively makes the prepared powder coating have excellent leveling performance and ensures the overall appearance quality of the coating. However, since the flexible monomer is introduced during the synthesis of the polyester resin, it is easy to cause the storage stability of the finished powder coating to be weakened. Therefore, in order to improve this problem, the present invention adds 1,4-cyclohexanedimethanol with a very stable cyclic structure to increase the glass transition temperature of the system, thereby solving the problem of poor storage stability of the powder coating. Therefore, the powder coating prepared by the present invention also has excellent storage stability.

[0080] Table 2

[0081] Test items Weather resistance UVB-313302h light retention rate (%) 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

[0082] It can be seen from Table 2 that the powder coating prepared by the present invention has outstanding weather resistance. This is because tert-butyl glycidyl carbonate and 2-butyl-2-ethyl-1,3-propanediol are added in the process of synthesizing the polyester resin to exert the steric hindrance effect and reduce the surface free energy of the coating; methylaminopropyl trimethoxysilane and triglycidyl isocyanurate are compounded as curing agents in the process of preparing the finished powder coating, so that a good network structure exists in the system; therefore, the powder coating prepared thereby has outstanding weather resistance.

[0083] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0084] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A highly weather-resistant polyester resin powder coating, characterized in that: Specifically comprising the following raw materials by weight: 80-90 parts by weight of homemade polyester resin 28-30 parts by weight of titanium dioxide 25-28 parts by weight of barium sulfate 8-10 parts by weight of curing agent 3-5 parts by weight of leveling agent 0.8-1 parts by weight of benzoin 0.4-0.6 parts by weight of auxiliary agent 3-6 parts by weight of pigment; The preparation method of the self-made polyester resin specifically comprises the following steps: Neopentyl glycol, 4,4'-(1-methylethylidene)dicyclohexanol, methylpropylene glycol, 1,4-cyclohexanedimethanol and 2-butyl-2-ethyl-1,3-propanediol are uniformly mixed and melted under temperature control; after the material is clarified, terephthalic acid, adipic acid, tertiary glycidyl carbonate and monobutyltin oxide are added in sequence; nitrogen is passed through and the temperature is slowly increased and maintained 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 maintained again, the acid value is measured twice, vacuum polycondensation is carried out, the acid value is measured three times, the material is vented, an antioxidant is added under temperature control, vacuum stirring and dispersion is carried out, and the material is discharged to obtain a self-made polyester resin; wherein the amount of the neopentyl glycol is 35-40 parts by weight, the amount of the 4,4'-(1-methylethylidene)bicyclohexanol is 5-8 parts by weight, the amount of the methylpropylene glycol is 6-6.5 parts by weight, the amount of the 1,4-cyclohexanedimethanol is 12-18 parts by weight, the amount of the 2-butyl-2-ethyl-1,3-propanediol is 8-12 parts by weight, the amount of the terephthalic acid is 55-65 parts by weight, the amount of the adipic acid is 10-15 parts by weight, the amount of the glycidyl versatate is 2-3 parts by weight, the amount of the monobutyltin oxide is 0.08-0.1 parts by weight, the amount of the isophthalic acid is 25-40 parts by weight, and the amount of the antioxidant is 0.5-1 parts by weight; The curing agent includes triglycidyl isocyanurate and methylaminopropyltrimethoxysilane; and the auxiliary agent is PE wax.

2. The highly weather-resistant polyester resin powder coating according to claim 1, characterized in that: The leveling agent includes a general leveling agent for powder coatings; the pigment includes at least one of mica iron oxide red, molybdenum chromium 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 coatings is GLP-503.

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

6. The highly weather-resistant polyester resin powder coating according to claim 5, characterized in that: The temperature of the temperature-controlled melting is 120-125° C.; the temperature of the heating and heat preservation 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 heat preservation is 238-240° C., and the time is 2-3 hours; 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 dispersion is 15-30 minutes.

7. A method for preparing a 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. Mix and crush 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, followed by tableting, cooling, crushing, screening, and packaging 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, wherein: The temperature of the temperature-controlled extrusion in step S2 is 100-110° C.; the average particle size of the powder after screening is 30-40 μm.

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