High-leveling impact-resistant bio-based polyester powder coating and preparation method thereof

Abstract

The invention provides a high-leveling impact-resistant bio-based polyester powder coating and a preparation method thereof, and belongs to the technical field of functional coatings. The bio-based powder coating comprises the following components in parts by mass: 60-80 parts of poly (neopentyl glycol terephthalate), 10-20 parts of polylactic acid, 0-10 parts of aliphatic-aromatic copolyester, 40-60 parts of titanium dioxide, 20-30 parts of barium sulfate, 6-8 parts of a curing agent, 2-4 parts of a toughening agent, 1-2 parts of a flatting agent, 1-2 parts of a brightening agent and 1-2 parts of benzoin. The preparation method comprises the following steps: carrying out melt blending on poly (neopentyl glycol terephthalate), polylactic acid and aliphatic-aromatic copolyester, carrying out mixing extrusion through a screw extruder, and drying to obtain blended resin; uniformly mixing the blended resin with a curing agent, a toughening agent, a flatting agent, a brightening agent, benzoin, titanium dioxide and barium sulfate, melting and blending in a screw extruder, crushing and sieving to obtain the bio-based polyester powder coating. The prepared powder coating is good in leveling performance during melting and curing, and the formed coating has the characteristics of high impact resistance, high bio-based content and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of functional coatings, and particularly relates to a high-leveling, impact-resistant bio-based polyester powder coating and a preparation method thereof. Background Art

[0002] As a solvent-free coating, powder coating has the advantages of being environmentally friendly and having high utilization rate, and is widely used in various coating fields. Traditional thermosetting powder coatings are mostly based on petroleum-based resins, such as epoxy resins, polyester resins, etc. Polyester resins are polymer compounds formed by the polycondensation of diols or dibasic acids or polyols and polyacids. They not only consume a large amount of non-renewable resources, but also cause environmental pollution during production and use. Bio-based polymer materials use biomass as raw materials, which can reduce carbon emissions during production and application. They are the development direction of polymer materials. The use of bio-based materials to manufacture bio-based powder coatings will also become the future development direction of the powder coating industry.

[0003] With the improvement of global environmental awareness, bio-based polymer materials are increasingly used in various fields. At present, countries around the world are in a technological revolution towards a sustainable economy, focusing on the development of bio-based products in almost all industries. Among them, polylactic acid (PLA), as a bio-based biodegradable thermoplastic aliphatic polyester, has become a hot spot for research and application due to its good biocompatibility and complete biodegradability. Its monomer raw materials can be obtained in large quantities from biomass. Due to its high strength similar to that of polystyrene, it is widely used in various fields. However, PLA is brittle, has low elongation at break, insufficient impact resistance, and the notched impact strength is usually less than 3 kJ / m², which greatly limits its wide application. In order to improve this property, it is necessary to introduce materials with flexible chains for modification, such as PBAT, PBS, and PBSA. PBAT, or polybutylene terephthalate-adipate, is a fully biodegradable thermoplastic polyester that combines the flexibility of polybutylene adipate (PBA) segments with the heat resistance and impact resistance of polybutylene terephthalate (PBT) segments. PBS, i.e. polybutylene succinate, has good toughness, tensile strength and heat resistance. PBSA, i.e. polybutylene succinate-adipate, has good flexibility and good fluidity and stability during the heating and forming process. Through the blended formulation system, the advantages of bio-based materials can be fully utilized, the synergistic enhancement of performance can be achieved, and key support can be provided for the performance improvement of bio-based powder coatings. Improving the compatibility between the blended resin components, improving the performance of polylactic acid, making it better meet the application requirements of powder coatings, and ensuring that the coating has good mechanical properties are the technical problems that need to be solved by the present invention. Summary of the invention

[0004] The present invention provides a high-leveling and impact-resistant bio-based polyester powder coating and a preparation method thereof. Through a melt extrusion blending process, materials such as polylactic acid, polyneopentyl terephthalate and aliphatic-aromatic copolyester are effectively compounded, and the intermolecular interaction during the melt blending of the blended resin is effectively regulated to improve the compatibility between the resin components, so as to prepare a high-leveling and impact-resistant bio-based powder coating that meets the requirements of industrial applications.

[0005] To achieve the above and other purposes, the present invention provides a high-leveling and impact-resistant bio-based polyester powder coating and a preparation method thereof, characterized in that the coating comprises at least the following components: 60-80 parts of polyneopentyl terephthalate; Polylactic acid 10-20 parts; Aliphatic-aromatic copolyester 0-10 parts; 40-60 parts of titanium dioxide; Barium sulfate 20-30 parts 2-4 parts of toughening agent; 6-8 parts of curing agent; 1-2 parts of leveling agent; 1-2 parts of brightener; 1-2 parts of benzoin.

[0006] In one embodiment of the present invention, the poly (neopentyl terephthalate) is prepared by condensation polymerization of terephthalic acid and neopentyl glycol and end-capped with terephthalic acid or isophthalic acid, has a molecular weight of 2000-5000 g / mol, a glass transition temperature of 60-70°C, an acid value of 30-35 mg KOH / g, and a viscosity of 3000-5000 mPa·s / 200°C.

[0007] In one embodiment of the present invention, the polylactic acid is hydroxy-terminated polylactic acid with a molecular weight of 5000-13000 g / mol, a glass transition temperature of 60-70°C, an acid value of 15-30 mg KOH / g, and a viscosity of 1000-5000 mPa·s / 200°C.

[0008] In one embodiment of the present invention, the aliphatic-aromatic copolyester is a mixture of one or more of polybutylene terephthalate-adipate, polybutylene succinate, and polybutylene succinate-adipate.

[0009] In one embodiment of the present invention, the high-leveling impact-resistant bio-based polyester powder coating is characterized in that the toughening agent is one or more of acrylic epoxy resins (Joncryl® ADR-4400, Joncryl® ADR4468).

[0010] In one embodiment of the present invention, the high-leveling and impact-resistant bio-based polyester powder coating is characterized in that the prepared bio-based polyester powder coating has high leveling when melt-cured, and the coating formed after curing has high impact resistance.

[0011] In one embodiment of the present invention, the high-leveling and impact-resistant bio-based polyester powder coating is characterized in that the preparation method comprises the following steps: (1) By melt blending technology, 60-80 parts of poly (neopentyl terephthalate), 10-20 parts of poly (lactic acid), and 0-10 parts of aliphatic-aromatic copolyester are mixed in a high-speed mixer at a speed of 1500-2000 r / min for 5-10 min, and the mixed materials are added into a twin-screw powder coating extruder according to metering, and the feeding zone I is set to 110°C, the mixing and extrusion zone II is set to 115°C, and the screw speed is 100-300 r / min. The materials are fully mixed and extruded under the push of the screw, and then dried to obtain a blended resin; (2) The blended resin prepared in step (1) is mixed with a curing agent, a toughening agent, a leveling agent, a brightener, benzoin, titanium dioxide, and barium sulfate in a high-speed mixer at a dispersing condition of 1000-2000 rpm for 5-10 min, and the mixed materials are added to a twin-screw powder coating extruder, the feeding zone I is set to 110°C, the mixing extrusion zone II is set to 115°C, the screw speed is 100-300 r / min, and the blend is melt-blended to obtain a blend, which is crushed and sieved through a 180-200 mesh screen to prepare a powder coating.

[0012] The present invention proposes a method for preparing a high-leveling impact-resistant bio-based polyester powder coating. The preparation process is simple to operate, and the toughening agent effectively improves the compatibility of heterogeneous components of the blended resin during melt blending, thereby significantly improving the impact resistance, flexibility and ductility of the prepared coating, making it less likely to crack or fall off when subjected to external forces, thereby extending the service life of the coating and meeting the application requirements of bio-based powder coating resins. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The impact performance effect diagram of the coatings made from the bio-based polyester powder coatings of Example 1, Example 3 and Example 6. DETAILED DESCRIPTION

[0014] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0015] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention are familiar to those skilled in the art and the description of the present invention, and any methods, equipment and materials of the prior art similar or equivalent to the methods, equipment and materials described in the embodiments of the present invention can also be used to implement the present invention.

[0016] Note that, unless otherwise specified, "%" and "part(s)" shown in the description herein mean "% by mass" and "part(s) by mass", respectively.

[0017] Hereinafter, the present invention will be explained in more detail by citing examples, which should not be construed as limiting. Appropriate modifications may be made within the scope consistent with the gist of the present invention, all of which fall within the technical scope of the present invention.

[0018] The raw materials, mass proportions and coating properties used in the preparation of bio-based polyester powder coatings in the following examples and comparative examples are shown in Table 1 and Table 2: Table 1. Composition and dosage of raw materials of bio-based polyester powder coatings in Examples 1-4 (proportion by mass)

[0019] Table 2. Coating properties of bio-based polyester powder coatings of Examples 1-4

[0020] Example 1

[0021] Referring to Table 1, the powder coating of this embodiment is prepared according to the following steps: Preparation of blended resin: polylactic acid, polyneopentyl terephthalate, and aliphatic-aromatic copolyester are added to a high-speed mixer and mixed at a speed of 1500-2000 r / min for 5-10 min. The obtained blend is compounded and extruded in a screw extruder. The feeding zone I is set to 110°C, the mixing and extrusion zone II is set to 115°C, the screw speed is 100-300 r / min, and the blended resin is obtained after drying.

[0022] Preparation of bio-based powder coating: The above blended resin and raw materials are mixed according to the ratio, and then mixed by a screw extruder, the feeding zone I is set to 110 ℃, the mixing and extrusion zone II is set to 115 ℃, the screw speed is 100-300 r / min, the extruded powder coating is put into a coffee grinder for grinding, and then sieved step by step, and the coating powder of 180-200 mesh is selected for spraying, and finally cured at 200 ℃ / 15 min. After the sample is prepared, the gel time, gloss, film thickness and impact performance are tested.

[0023] Example 2

[0024] The raw materials and formula of the bio-based polyester powder coating used in this example are shown in Table 1, and the preparation process is the same as that in Example 1.

[0025] Example 3

[0026] The raw materials and formula of the bio-based polyester powder coating used in this example are shown in Table 1, and the preparation process is the same as that in Example 1.

[0027] Example 4

[0028] The raw materials and formula of the bio-based polyester powder coating used in this example are shown in Table 1, and the preparation process is the same as that in Example 1.

[0029] The bio-based polyester powder coatings prepared in the above embodiments were tested, wherein the test standards were: The gel time is tested according to GB / T 16995-1997.

[0030] Gloss: tested according to GB / T 9754-2007 standard.

[0031] Impact performance is tested according to GB / T 1732-1993 standard.

[0032] As shown in Table 2, the various properties of the powder coatings in Example 1 and Examples 2-4 are compared. Among them, polylactic acid with a molecular weight of 60,000 is added to the powder coating in Example 1, and polylactic acid with molecular weights of 5,000, 7,000 and 13,000 is added to Examples 2-4. The test performance of the powder coating coating in Examples 2-4 is significantly better than that in Example 1, and Example 3 has the best impact performance. After withstanding a 50 cm drop hammer impact, the forward impact passes, but the recoil produces cracks, and the reverse impact fails. It can be seen that the molecular weight of the introduced polylactic acid has a great influence on the physical properties of the powder coating, and the impact strength fails to pass the test. At the same time, when the molecular weight of the polylactic acid is too large, the leveling of the powder coating is poor, and severe orange stripes appear.

[0033] In order to prepare a bio-based powder coating that meets industrial requirements, the raw materials, mass proportions and coating properties used in preparing the bio-based polyester powder coating in the following examples are shown in Table 3 and Table 4: Table 3, Example 3 and Example 5-7 Bio-based polyester powder coating raw material composition and dosage (by mass proportion)

[0034] Table 4, coating properties of bio-based polyester powder coatings in Examples 3 and 5-7

[0035] Example 5

[0036] The raw materials and formula of the bio-based polyester powder coating used in this example are shown in Table 3, and the preparation process is the same as that in Example 1.

[0037] Example 6

[0038] The raw materials and formula of the bio-based polyester powder coating used in this example are shown in Table 3, and the preparation process is the same as that in Example 1.

[0039] Example 7

[0040] The raw materials and formula of the bio-based polyester powder coating used in this example are shown in Table 3, and the preparation process is the same as that in Example 1.

[0041] The bio-based polyester powder coatings prepared in the above embodiments were tested, wherein the test standards were: The gel time is tested according to GB / T 16995-1997.

[0042] Gloss: tested according to GB / T 9754-2007 standard.

[0043] Impact performance is tested according to GB / T 1732-1993 standard.

[0044] As shown in Table 4, the various properties of the powder coatings in Example 3 and Examples 5-7 are compared. Among them, the powder coating in Example 3 adds polylactic acid with a molecular weight of 7000, and in Examples 5-7, polylactic acid with a molecular weight of 7000, different proportions of aliphatic-aromatic copolyesters and 1% toughening agent are added. The powder coating in Example 6 performs best. When the impact performance is tested, it withstands a 50 cm drop hammer impact without obvious shedding and cracking, and passes both the forward impact and the recoil impact. The results are as follows Figure 1 As shown, the addition of aliphatic-aromatic copolyester and toughening agent can significantly improve the strength and toughness of powder coatings. The bio-based carbon content of the prepared powder coatings reaches 15%, while retaining other excellent mechanical properties.

[0045] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0046] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A high-leveling, impact-resistant bio-based polyester powder coating, characterized in that: The bio-based polyester powder coating comprises at least the following components by weight: 60-80 parts of polyneopentyl terephthalate; Polylactic acid 10-20 parts; Aliphatic-aromatic copolyester 0-10 parts; 40-60 parts of titanium dioxide; Barium sulfate 20-30 parts 2-4 parts of toughening agent; 6-8 parts of curing agent; 1-2 parts of leveling agent; 1-2 parts of brightener; 1-2 parts of benzoin.

2. A high-leveling, impact-resistant bio-based polyester powder coating according to claim 1, characterized in that: The poly (neopentyl terephthalate) is prepared by condensation polymerization of terephthalic acid and neopentyl glycol and end-capped with terephthalic acid or isophthalic acid. It has a molecular weight of 2000-5000 g / mol, a glass transition temperature of 60-70°C, an acid value of 30-35 mg KOH / g, and a viscosity of 3000-5000 mPa·s / 200°C.

3. The high-leveling, impact-resistant bio-based polyester powder coating according to claim 1, characterized in that: The polylactic acid is carboxyl-terminated polylactic acid with a molecular weight of 5000-13000 g / mol, a glass transition temperature of 60-70°C, an acid value of 15-30 mg KOH / g, and a viscosity of 1000-5000 mPa·s / 200°C.

4. The high-leveling, impact-resistant bio-based polyester powder coating according to claim 1, characterized in that: The aliphatic-aromatic copolyester is a mixture of polybutylene terephthalate-adipate, polybutylene succinate, polybutylene succinate-adipate or a mixture thereof.

5. The high-leveling, impact-resistant bio-based polyester powder coating according to claim 1, characterized in that: The toughening agent is one or more of acrylic epoxy resins (Joncryl® ADR-4400, Joncryl® ADR4468).

6. The high-leveling, impact-resistant bio-based polyester powder coating according to claim 1, characterized in that The prepared bio-based polyester powder coating has high leveling during melt solidification, and the coating formed after solidification has high impact resistance.

7. The high-leveling, impact-resistant bio-based polyester powder coating according to claim 1, characterized in that: The preparation method comprises the following steps: (1) By melt blending technology, 60-80 parts of poly (neopentyl terephthalate), 10-20 parts of poly (lactic acid), and 0-10 parts of aliphatic-aromatic copolyester are mixed in a high-speed mixer at a speed of 1500-2000 r / min for 5-10 min, and the mixed materials are added into a twin-screw powder coating extruder according to metering, and the feeding zone I is set to 110°C, the mixing and extrusion zone II is set to 115°C, and the screw speed is 100-300 r / min. The materials are fully mixed and extruded under the push of the screw, and then dried to obtain a blended resin; (2) The blended resin prepared in step (1) is mixed with a curing agent, a toughening agent, a leveling agent, a brightener, benzoin, titanium dioxide, and barium sulfate in a high-speed mixer at a dispersing condition of 1000-2000 rpm for 5-10 min, and the mixed materials are added to a twin-screw powder coating extruder, the feeding zone I is set to 110°C, the mixing extrusion zone II is set to 115°C, the screw speed is 100-300 r / min, and the blend is melt-blended to obtain a blend, which is crushed and sieved through a 180-200 mesh screen to prepare a powder coating.

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