A bio-based coating and a preparation method thereof

Abstract

The present invention relates to a bio-based coating and a preparation method thereof. The preparation method comprises the following steps: mixing furandicarboxylic acid with diol, heating and refluxing reaction under the action of a catalyst; adding a polyacid end-capping agent, keeping the temperature to react, and obtaining a polyester resin; carrying out a polycondensation reaction of castor oil and dicarboxylic acid under the action of an aluminum salt catalyst to obtain a castor oil-based resin; mixing the polyester resin, castor oil-based resin, filler, and inorganic pigment uniformly to obtain a resin mixture, and then adding a curing agent and an auxiliary agent and stirring uniformly; wherein the mass ratio of the polyester resin to the resin mixture does not exceed 18%. The coating product of the present invention has excellent mechanical properties and aging resistance, and the adhesion of the product is also greatly improved, and has good application prospects.

Description

Technical Field

[0001] The invention relates to the field of coatings, and in particular to a bio-based coating and a preparation method thereof. Background Art

[0002] With the development of social economy, people's living standards are getting higher and higher, people's awareness of healthy living is improving, and increasingly stringent environmental protection regulations have put forward higher and higher requirements for the development of coatings, making the application of traditional coatings more and more restricted, making modern coatings develop in the direction of high performance, high efficiency, high environmental protection and high decorativeness.

[0003] The raw materials used in existing coating resins all come from petrochemical products, and petrochemical materials are non-renewable. With the continuous increase in human consumption, the storage capacity of petrochemical materials will become less and less, and will eventually be exhausted. In order to achieve sustainable development, it is necessary to develop and utilize sustainable raw materials to replace existing petrochemical raw materials. Therefore, replacing part of the petrochemical raw materials with bio-based raw materials to prepare coating resins will become the future development direction. In the Chinese patent application with publication number CN107163234A, it is proposed to completely replace petrochemical raw material polyols and polyacids with bio-based polyols and bio-based polyacids, but due to the use of a single bio-based polyol and polyacid to prepare the powder coating resin, its performance will be greatly affected, especially the mechanical properties, aging resistance and adhesion, etc., which cannot be compared with the existing products prepared using petrochemical raw materials. Summary of the invention

[0004] The purpose of the present invention is to provide a bio-based coating and a preparation method thereof in order to overcome the defects of the above-mentioned prior art. The coating obtained by the preparation method is compounded with castor oil-based resin and furandicarboxylic acid polyester resin, which not only improves the mechanical properties and aging resistance of the coating product, but also greatly improves the adhesion of the product, and has good application prospects.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] A method for preparing a bio-based coating comprises the following steps:

[0007] (1) mixing furandicarboxylic acid and diol, heating and refluxing reaction under the action of a catalyst; adding a polyacid end-capping agent, keeping the temperature to react, and obtaining a polyester resin;

[0008] (2) subjecting castor oil and dicarboxylic acid to a polycondensation reaction under the action of an aluminum salt catalyst to obtain a castor oil-based resin;

[0009] (3) The polyester resin, castor oil-based resin, filler and inorganic pigment are mixed uniformly to obtain a resin mixture, and then a curing agent and an auxiliary agent are added and stirred uniformly; wherein the mass ratio of the polyester resin to the resin mixture does not exceed 18%.

[0010] Among them, step (1) is preferably performed as follows: first, add the diol into the reaction kettle, introduce nitrogen and heat to 130-150°C, add furandicarboxylic acid and a catalyst, continue to heat to 160-200°C to start the esterification reaction for 3-5 hours, then heat to 230-250°C and continue the esterification reaction for 10-12 hours. When the acid value reaches 10-15 mgKOH / g, add a polyacid capping agent under nitrogen protection, stir the reaction at 240-250°C for 2-3 hours, and when the acid value reaches 60-70 mgKOH / g, the reaction is completed.

[0011] Among them, the diol is preferably one or more of ethylene glycol, propylene glycol, diethylene glycol and neopentyl glycol.

[0012] In step (1), the molar ratio of furandicarboxylic acid to diol is preferably 1:1 to 1.1:1.

[0013] Wherein, the polyacid end-capping agent is preferably one or more of trimellitic anhydride, pyromellitic anhydride and adipic acid.

[0014] Wherein, in the preparation method of the polyester resin, the catalyst is preferably a tin catalyst, more preferably monobutyltin oxide or stannous oxalate.

[0015] Preferably, in step (2), the reaction temperature of the polycondensation reaction is 110°C to 130°C, and the reaction time is 3 to 5 hours;

[0016] Wherein, the dicarboxylic acid is preferably one or more of succinic acid, adipic acid and suberic acid.

[0017] Wherein, in the preparation method of castor oil-based resin, the aluminum salt catalyst is preferably aluminum trichloride or aluminum sulfate.

[0018] In step (2), the molar ratio of castor oil to dicarboxylic acid is preferably 1:1 to 1.2:1.

[0019] Wherein, the filler is preferably one or more of organic bentonite, calcium carbonate and talc.

[0020] Among them, the inorganic pigment is preferably one or more of titanium dioxide, red iron oxide, yellow iron oxide and iron blue.

[0021] Wherein, the curing agent is preferably triglycidyl isocyanurate (TGIC).

[0022] Among them, the auxiliary agent is preferably a leveling agent and a brightening agent.

[0023] The polyester resin preferably accounts for 3-18% by weight of the resin mixture, and more preferably 8-16% by weight.

[0024] The present invention also provides a bio-based coating prepared by the above preparation method.

[0025] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts castor oil-based resin and furandicarboxylic acid polyester resin to compound, which not only improves the mechanical properties and aging resistance of the coating product, but also greatly improves the adhesion of the product, and has good application prospects. Implementation

[0026] The present invention is described in detail below with reference to specific embodiments. Example

[0027] The bio-based coating of this example was prepared by the following method:

[0028] (1) First, add diol (ethylene glycol) into a reactor, introduce nitrogen and heat to 130°C, add furandicarboxylic acid and a catalyst (monobutyltin oxide), continue to heat to 180°C to start esterification reaction for 5 hours, then heat to 230°C to continue esterification reaction for 12 hours, and when the acid value reaches 10 mgKOH / g, add a polyacid end-capping agent (trimellitic anhydride) under nitrogen protection, stir and react at 240°C for 2 hours, and stop the reaction when the acid value reaches 60 mgKOH / g to obtain a terminal acid polyester resin; in this step, the molar ratio of furandicarboxylic acid to diol is 1:1;

[0029] (2) 0.5 mol of castor oil, 0.5 mol of succinic acid and 0.2 g of aluminum chloride were added into a three-necked flask, and polycondensed for 3 hours at 120° C. with mechanical stirring to obtain a castor oil-based resin;

[0030] (3) Mix 4 g of polyester resin, 18 g of castor oil-based resin, 2 g of filler (organic bentonite), and 1 g of inorganic pigment (titanium dioxide) to obtain a resin mixture, then add 1 g of curing agent (triglycidyl isocyanurate TGIC) and 0.2 g of auxiliary agent (leveling agent) and stir evenly to obtain a bio-based coating. Example

[0031] The bio-based coating of this example was prepared by the following method:

[0032] (1) First, add diol (propylene glycol) into a reaction kettle, introduce nitrogen and heat to 140°C, add furandicarboxylic acid and a catalyst (stannous oxalate), continue to heat to 190°C to start esterification reaction for 4 hours, then heat to 240°C to continue esterification reaction for 12 hours, and when the acid value reaches 15 mgKOH / g, add a polyacid end-capping agent (pyromellitic anhydride) under nitrogen protection, stir and react at 250°C for 2 hours, and stop the reaction when the acid value reaches 65 mgKOH / g to obtain a terminal acid polyester resin; in this step, the molar ratio of furandicarboxylic acid to diol is 1:1;

[0033] (2) 0.55 mol of castor oil, 0.5 mol of adipic acid and 0.2 g of aluminum sulfate were added into a three-necked flask, and polycondensed under mechanical stirring at 120° C. for 4 hours to obtain a castor oil-based resin;

[0034] (3) Mix 3 g of polyester resin, 18 g of castor oil-based resin, 2 g of filler (calcium carbonate), and 1 g of inorganic pigment (red iron oxide) to obtain a resin mixture, then add 1 g of curing agent (triglycidyl isocyanurate TGIC) and 0.2 g of auxiliary agent (leveling agent) and stir evenly to obtain a bio-based coating. Example

[0035] The bio-based coating of this example was prepared by the following method:

[0036] (1) First, add diol (neopentyl glycol) into a reaction kettle, introduce nitrogen and heat to 150°C, add furandicarboxylic acid and a catalyst (stannous oxalate), continue to heat to 200°C to start esterification reaction for 5 hours, then heat to 250°C to continue esterification reaction for 12 hours, and when the acid value reaches 15 mgKOH / g, add a polyacid end-capping agent (adipic acid) under nitrogen protection, stir and react at 250°C for 2 hours, and stop the reaction when the acid value reaches 70 mgKOH / g to obtain a terminal acid polyester resin; in this step, the molar ratio of furandicarboxylic acid to diol is 1:1;

[0037] (2) 0.6 mol of castor oil, 0.5 mol of adipic acid and 0.2 g of aluminum sulfate were added into a three-necked flask, and polycondensed under mechanical stirring at 130° C. for 4 hours to obtain a castor oil-based resin;

[0038] (3) Mix 2 g of polyester resin, 18 g of castor oil-based resin, 2 g of filler (calcium carbonate), and 1 g of inorganic pigment (red iron oxide) to obtain a resin mixture, then add 1 g of curing agent (triglycidyl isocyanurate TGIC) and 0.2 g of auxiliary agent (leveling agent) and stir evenly to obtain a bio-based coating.

[0039] Comparative Example 1

[0040] The preparation method of this comparative example is the same as that of Example 1, except that in step (3), the amount of polyester resin used is 6 g, the amount of castor oil-based resin is 18 g, the amount of filler (organic bentonite) is 2 g, and the amount of inorganic pigment (titanium dioxide) is 1 g. The other conditions remain unchanged to obtain a bio-based coating.

[0041] Comparative Example 2

[0042] The bio-based coating of this comparative example was prepared by the following method:

[0043] (1) First, add diol (ethylene glycol) into a reactor, introduce nitrogen and heat to 130°C, add furandicarboxylic acid and a catalyst (monobutyltin oxide), continue to heat to 180°C to start esterification reaction for 5 hours, then heat to 230°C to continue esterification reaction for 12 hours, and when the acid value reaches 10 mgKOH / g, add a polyacid end-capping agent (trimellitic anhydride) under nitrogen protection, stir and react at 240°C for 2 hours, and stop the reaction when the acid value reaches 60 mgKOH / g to obtain a terminal acid polyester resin; in this step, the molar ratio of furandicarboxylic acid to diol is 1:1;

[0044] (2) Mix 4 g of polyester resin, 2 g of filler (organic bentonite), and 1 g of inorganic pigment (titanium dioxide) to obtain a resin mixture, then add 1 g of curing agent (triglycidyl isocyanurate TGIC) and 0.2 g of auxiliary agent (leveling agent) and stir evenly to obtain a bio-based coating. Example

[0045] The coating powder obtained in the above example was melt-extruded by a twin-screw extruder, tableted, cooled, crushed, and sieved, and then sprayed on the surface-treated tinplate substrate using an electrostatic spray gun, and cured at 200° C. / 10 min to obtain a polyester powder coating.

[0046] Coating testing standards:

[0047] The storage stability test condition is baking in an oven at 42°C for 24 hours; the 60° gloss test is based on GB / T9754-2007; the impact strength test is based on GB / T 1732-1993; the leveling grade test is based on the leveling performance rating according to the leveling effect rating standard version of the US PCI; the coating appearance test is based on visual observation; the heat resistance test condition is baking in an oven at 350°C for 48 hours; the coating weather resistance test is based on GB / T14522-2008.

[0048] The coating performance test is shown in the following table.

[0049] ;

[0050] It can be seen from the above experimental data that after the comparative example coating was boiled in high pressure water for 2 hours, a large number of bubbles appeared on the coating film, which would reduce the adhesion of the coating film. The curing shrinkage of the comparative example reached more than 9%. Too much curing shrinkage would affect the adhesion of the resin coating to the substrate, which also confirmed the above adhesion test results. The bio-based coating prepared by the embodiment of the present invention has good heat resistance, mechanical properties and bonding properties, and the product has excellent comprehensive performance.

[0051] It must be emphasized that the above detailed description is a specific description of a feasible embodiment of the present invention, but the embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the technical spirit of the present invention should be included in the patent scope of the present invention.

Claims

1. A method for preparing a bio-based coating, comprising the following steps: (1) mixing furandicarboxylic acid and diol, heating and refluxing reaction under the action of a catalyst; adding a polyacid end-capping agent, keeping the temperature to react, and obtaining a polyester resin; (2) subjecting castor oil and dicarboxylic acid to a polycondensation reaction under the action of an aluminum salt catalyst to obtain a castor oil-based resin; (3) The polyester resin, castor oil-based resin, filler and inorganic pigment are mixed evenly to obtain a resin mixture, and then a curing agent and an auxiliary agent are added and stirred evenly; wherein: The mass ratio of the polyester resin to the resin mixture does not exceed 18%.

2. The preparation method according to claim 1, characterized in that Step (1) adopts the following steps: firstly, add the diol into the reaction kettle, introduce nitrogen and heat to 130-150°C, add furandicarboxylic acid and catalyst, continue to heat to 160-200°C to start esterification reaction for 3-5 hours, then heat to 230-250°C to continue esterification reaction for 10-12 hours, when the acid value reaches 10-15 mgKOH / g, add the polyacid end-capping agent under nitrogen protection, stir and react at 240-250°C for 2-3 hours, and when the acid value reaches 60-70 mgKOH / g, the reaction is completed.

3. The preparation method according to claim 1, characterized in that: The diol is one or more of ethylene glycol, propylene glycol, diethylene glycol and neopentyl glycol; In step (1), the molar ratio of furandicarboxylic acid to diol is 1:1 to 1.1:

1.

4. The preparation method according to claim 1, characterized in that: The polyacid end-capping agent is one or more of trimellitic anhydride, pyromellitic anhydride and adipic acid; In the preparation method of the polyester resin, the catalyst is a tin catalyst.

5. The preparation method according to claim 4, characterized in that: In the preparation method of the polyester resin, the catalyst is monobutyltin oxide or stannous oxalate.

6. The preparation method according to claim 1, characterized in that: In step (2), the reaction temperature of the polycondensation reaction is 110° C. to 130° C., and the reaction time is 3 to 5 hours; the dicarboxylic acid is one or more of succinic acid, adipic acid and suberic acid.

7. The preparation method according to claim 1, characterized in that: In the method for preparing castor oil-based resin, the aluminum salt catalyst is aluminum trichloride or aluminum sulfate.

8. The preparation method according to claim 1, characterized in that: In step (2), the molar ratio of castor oil to dicarboxylic acid is 1:1 to 1.2:

1.

9. The preparation method according to claim 1, characterized in that: The filler is one or more of organic bentonite, calcium carbonate and talcum powder; the inorganic pigment is one or more of titanium dioxide, red iron oxide, yellow iron oxide and iron blue.

10. The preparation method according to claim 1, characterized in that: The curing agent is triglycidyl isocyanurate.

11. A bio-based coating prepared by the preparation method according to any one of claims 1 to 10.