A process for the preparation of a fluorine-containing polyurethane coating

Abstract

The application discloses a preparation method of fluorine-containing polyurethane paint and belongs to the technical field of polyurethane paint. The preparation method comprises the following raw materials in parts by weight: 30-50 parts of diphenylmethane diisocyanate, 20-30 parts of polybutylene adipate glycol, 25-35 parts of polypropylene glycol, 0.5-1.5 parts of a catalyst, 6-18 parts of modified dihydric alcohol, 100-150 parts of acetone, 2-4 parts of 1,4-butanediol, 3-5 parts of dimethylol propionic acid, 120-180 parts of deionized water and 3-6 parts of a defoaming agent. The paint uses water as a solvent, and environmental pollution is small. The modified dihydric alcohol contains fluorine elements and various functional groups, and the paint has enhanced flame retardance, heat resistance, waterproofness and corrosion resistance, and is stable in performance. Therefore, the fluorine-containing polyurethane paint prepared by the application has stable and efficient flame retardance, heat resistance, waterproofness and corrosion resistance, is environment-friendly, and has important application value in the technical field of polyurethane paint.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyurethane coatings, and particularly relates to a preparation method of fluorine-containing polyurethane coatings. BACKGROUND

[0002] Polyurethane coatings are a coating technology that began to rise in the 1960s, have excellent wear resistance, strong adhesion, excellent chemical resistance and oil resistance, urethane bonds do not react with acids, bases and oils, high reactivity (low temperature curing performance), and high decoration and protection performance. Due to its excellent performance, it has been widely used in the fields of industrial protection, wooden furniture, automobile coatings, construction industry and environmental protection coatings.

[0003] With the development of social economy and technology, people have more and more demands for high-quality and multi-functional materials, and the requirements for the water resistance, oil resistance and antifouling effect of materials are also higher and higher in many fields, especially in the field of coatings. Traditional polyurethane coatings have been unable to meet people's demands.

[0004] Now there are studies on introducing fluorine elements into polyurethane to make fluorine-containing polyurethane coatings, which not only can maintain the original characteristics of polyurethane, but also can endow the fluorine-containing polyurethane coatings with excellent thermal stability, weather resistance and chemical inertness, unique low surface free energy and low friction coefficient, and very significantly enhanced performance of polyurethane coatings due to the strong electronegativity of fluorine, high C-F bond energy (540 kJ / mol), smallest van der Waals radius except hydrogen and the shielding protection of fluorine to carbon chain. However, the current fluorine-containing finishing agent cannot provide flame retardant performance, the oxygen index of polyurethane itself is low, the flame retardant performance is poor, the addition of additional flame retardant will inevitably affect the homogeneity of polyurethane, and the small molecule flame retardant is easy to migrate and seep out, resulting in the loss of flame retardant performance. Furthermore, most of the polyurethane coatings on the market are solvent-based, which are favored by consumers due to their excellent hardness, film fullness, excellent chemical resistance and fast drying, but the use of organic solvents such as benzene, toluene and xylene leads to excessive VOC, causing resource waste and environmental pollution, and limiting the application of polyurethane coatings. Therefore, it is urgent to solve the above problems to meet the higher demands in the technical field of polyurethane coatings. SUMMARY

[0005] The purpose of the present application is to overcome the defects of the prior art and provide a preparation method of fluorine-containing polyurethane coatings.

[0006] The purpose of the present application can be achieved by the following technical solutions.

[0007] A preparation method of fluorine-containing polyurethane coatings, comprising the following steps:

[0008] In a reaction kettle, diphenylmethane diisocyanate (MDI) preheated to 50-60℃ is added, then nitrogen gas is introduced as a protective gas, polybutylene adipate glycol, polypropylene glycol (PPG), catalyst, modified diol and acetone are added and stirred to mix uniformly, after reaction at 50-60℃ for 2-4h; 1,4-butanediol (BDO, chain extender) and dimethylol propionic acid (hydrophilic chain extender) are added, and refluxed at 60-70℃ for 4-6h; after the reaction is completed, deionized water and defoaming agent are added, and high-speed shearing emulsification is carried out for 30-60min, and acetone is removed by distillation under reduced pressure to obtain a fluorine-containing polyurethane coating.

[0009] Further, each raw material is as follows in terms of weight parts: 30-50 parts of diphenylmethane diisocyanate, 20-30 parts of polybutylene adipate glycol, 25-35 parts of polypropylene glycol, 0.5-1.5 parts of catalyst, 6-18 parts of modified diol, 100-150 parts of acetone, 2-4 parts of 1,4-butanediol, 3-5 parts of dimethylol propionic acid, 120-180 parts of deionized water, and 3-6 parts of defoaming agent.

[0010] Further, the defoaming agent is a silicone defoaming agent.

[0011] Further, the catalyst is one of stannous octoate and dibutyl tin oxide.

[0012] Further, the modified diol is prepared by the following steps:

[0013] S1, a three-necked flask equipped with a stirring device is added with melamine, diethyl phosphoacetic acid, dicyclohexyl carbodiimide (DCC, dehydrating agent) and N,N-dimethylformamide (DMF), after stirring and mixing uniformly, it is placed in a water bath at 55℃, and heated in a water bath for 6h, after the reaction is completed, it is filtered, the solvent is removed by distillation under reduced pressure, washed with pyridine for 2-3 times, and vacuum dried to obtain intermediate 1; the ratio of the amounts of melamine, diethyl phosphoacetic acid, dicyclohexyl carbodiimide and N,N-dimethylformamide is 14.3g:19.6g:20.6g:120mL;

[0014] Under the action of dicyclohexyl carbodiimide, the amidation reaction of melamine and diethyl phosphoacetic acid occurs, by controlling the molar ratio of the two to be close to 1:1 and the melamine to be slightly excessive, intermediate 1 is obtained; the specific reaction process is as follows:

[0015]

[0016] S2, in a three-necked flask equipped with stirring device, hexafluoroglutaroyl chloride, aluminum chloride (catalyst) and N, N-dimethylformamide were mixed and stirred constantly until mixed evenly, then 3-amino-1-propanol was added dropwise, after the dropwise addition was completed, the device was incubated in 40℃ water bath for 3h, the reaction was completed, filtered, the solvent was removed by reduced pressure distillation, to obtain intermediate 2; the ratio of the amount of hexafluoroglutaroyl chloride, aluminum chloride, N, N-3-amino-1-propanol was 28.7g: 0.4g: 100mL: 7.5g;

[0017] Under the catalysis of aluminum chloride, hexafluoroglutaroyl chloride and 3-amino-1-propanol occurred amidation reaction, by controlling the molar ratio of the two close to 1:1 and hexafluoroglutaroyl chloride slightly excess, to obtain intermediate 2; the specific reaction process is as follows:

[0018]

[0019] S3, in a three-necked flask equipped with stirring device, intermediate 2, intermediate 1 and N, N-dimethylformamide were mixed and stirred evenly, then aluminum chloride was added, the device was incubated in 55℃ water bath for 6h, the reaction was completed, filtered, part of the solvent was removed by rotary evaporation, then purified by column chromatography (eluent using petroleum ether / ethyl acetate mixed solvent, the volume ratio of the two was 5:1), the eluent was removed by rotary evaporation, to obtain modified diol; the ratio of the amount of intermediate 2, intermediate 1, N, N-dimethylformamide, aluminum chloride was 67.3g: 30.4g: 200mL: 0.9g;

[0020] Under the catalysis of aluminum chloride, intermediate 2 and intermediate 1 occurred amidation reaction, by controlling the molar ratio of the two close to 2:1 and intermediate 2, to obtain modified diol; the specific reaction process is as follows:

[0021]

[0022] The prepared modified dihydric alcohol can participate in the isocyanate polymerization reaction under the action of a catalyst due to containing two hydroxyl groups in the molecule, is connected to the polyurethane macromolecular chain, and makes the modified dihydric alcohol not easy to separate out and exude, thereby ensuring the stability of the modified dihydric alcohol. In addition, the modified dihydric alcohol molecule further contains phosphate, triazine, C-F bond and amide group structures. The phosphate belongs to a phosphorus-based flame retardant, and can enhance the flame retardant property of the polyurethane matrix by realizing the flame retardant effect through the gas phase flame retardant mechanism and the condensed phase flame retardant mechanism. The introduced triazine structure is a nitrogen-based flame retardant, and can generate nitrogen-containing gas during combustion to dilute and reduce the smoke density, and form melamine at high temperature to make the carbon layer compact, thereby greatly enhancing the flame retardant property of the matrix. The introduced fluorine element has small polarity and high bond energy, and good stability, can shield and protect the carbon chain, reduce the surface free energy of the matrix, and significantly improve the heat resistance, water resistance and corrosion resistance of the matrix. Finally, the modified dihydric alcohol molecule contains a large amount of amide groups, and the amide group is a hydrophobic group, which can further improve the water resistance of the matrix.

[0023] The beneficial effects of the present application are as follows:

[0024] 1. The polyurethane coating prepared by the present application uses water as a solvent, and has low VOC content and small environmental pollution compared with solvent-based polyurethane coatings.

[0025] 2. The prepared modified dihydric alcohol contains fluorine elements and various functional groups, which can have a synergistic effect, significantly enhance the flame retardancy, heat resistance, water resistance and corrosion resistance of the coating, and be connected to the polyurethane macromolecular chain, not easy to fall off, and have long-term stable performance.

[0026] Therefore, the present application prepares a modified dihydric alcohol containing fluorine through three steps, and uses the modified dihydric alcohol as a raw material to prepare a fluorine-containing polyurethane coating. The prepared coating has stable and efficient flame retardancy, heat resistance, water resistance and corrosion resistance, is water-based and environmentally friendly, and has important application value in the polyurethane coating technical field. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0028] Embodiment one

[0029] Preparation of modified dihydric alcohol:

[0030] S1, in a three-necked flask equipped with stirring device, 14.3g melamine, 19.6g diethyl phosphoacetic acid, 20.6g dicyclohexyl carbodiimide and 120ml N,N-dimethylformamide were added, after stirring and mixing uniformly, the device was placed in a water bath at 55℃, and heated for 6h, after the reaction was completed, filtration, removal of solvent by reduced pressure distillation, washed with pyridine for 2-3 times, vacuum drying, to obtain intermediate 1;

[0031] S2, in a three-necked flask equipped with stirring device, 28.7g hexafluoroglutaric chloride, 0.4g aluminum chloride and 100ml N,N-dimethylformamide were mixed and stirred constantly until uniformly mixed, then 7.5g 3-amino-1-propanol was added dropwise, after the dropwise addition was completed, the device was incubated in a water bath at 40℃ for 3h, after the reaction was completed, filtration, removal of solvent by reduced pressure distillation, to obtain intermediate 2;

[0032] S3, in a three-necked flask equipped with stirring device, 67.3g intermediate 2, 30.4g intermediate 1 and 200ml N,N-dimethylformamide were mixed and stirred uniformly, then 0.9g aluminum chloride was added, the device was placed in a water bath at 55℃ for incubation and reaction for 6h, after the reaction was completed, filtration, removal of part of the solvent by rotary evaporation, then purified by column chromatography (eluent: mixed solvent of petroleum ether / ethyl acetate, volume ratio of 5:1), removal of the eluent by rotary evaporation, to obtain modified diol.

[0033] Example two

[0034] Preparation of modified diol:

[0035] S1, in a three-necked flask equipped with stirring device, 28.6g melamine, 39.2g diethyl phosphoacetic acid, 41.2g dicyclohexyl carbodiimide and 240ml N,N-dimethylformamide were added, after stirring and mixing uniformly, the device was placed in a water bath at 55℃, and heated for 6h, after the reaction was completed, filtration, removal of solvent by reduced pressure distillation, washed with pyridine for 2 times, vacuum drying, to obtain intermediate 1;

[0036] S2, in a three-necked flask equipped with stirring device, 57.4g hexafluoroglutaric chloride, 0.8g aluminum chloride and 200ml N,N-dimethylformamide were mixed and stirred constantly until uniformly mixed, then 15.0g 3-amino-1-propanol was added dropwise, after the dropwise addition was completed, the device was incubated in a water bath at 40℃ for 3h, after the reaction was completed, filtration, removal of solvent by reduced pressure distillation, to obtain intermediate 2;

[0037] S3, in a three-mouth flask equipped with stirring device, 134.6 g of intermediate 2, 60.8 g of intermediate 1 and 400 ml of N, N-dimethylformamide were mixed and stirred uniformly, then 1.8 g of aluminum chloride was added, the device was placed in a 55 °C water bath for 6 h, the reaction was completed, filtered, rotary evaporation to remove part of the solvent, then purified by column chromatography (eluent using petroleum ether / ethyl acetate mixed solvent, the volume ratio of the two is 5:1), rotary evaporation to remove the eluent, to obtain the modified diol.

[0038] Example three

[0039] In the reaction kettle, 30 g of diphenyl methane diisocyanate preheated to 50 °C was added, then nitrogen was introduced as a protective gas, 20 g of polybutylene adipate glycol, 25 g of polypropylene glycol, 0.5 g of stannous octoate, 6 g of modified diol prepared by example one and 100 g of acetone were stirred and mixed uniformly, reacted at 50 °C for 2 h; 2 g of 1, 4-butanediol and 3 g of dimethylol propionic acid were added, and refluxed at 60 °C for 4 h; after the reaction was completed, 120 g of deionized water and 3 g of defoamer silicone defoamer were added, and high-speed shear emulsification was carried out for 30 min, then acetone was removed by distillation under reduced pressure to obtain a fluorine-containing polyurethane coating.

[0040] Example four

[0041] In the reaction kettle, 40 g of diphenyl methane diisocyanate preheated to 55 °C was added, then nitrogen was introduced as a protective gas, 25 g of polybutylene adipate glycol, 30 g of polypropylene glycol, 1.0 g of dibutyl tin oxide, 12 g of modified diol prepared by example one and 125 g of acetone were stirred and mixed uniformly, reacted at 55 °C for 3 h; 3 g of 1, 4-butanediol and 4 g of dimethylol propionic acid were added, and refluxed at 65 °C for 5 h; after the reaction was completed, 150 g of deionized water and 5 g of defoamer silicone defoamer were added, and high-speed shear emulsification was carried out for 45 min, then acetone was removed by distillation under reduced pressure to obtain a fluorine-containing polyurethane coating.

[0042] Example five

[0043] In the reaction kettle, 50 g of diphenyl methane diisocyanate preheated to 60 °C was added, then nitrogen was introduced as a protective gas, 30 g of polybutylene adipate glycol, 35 g of polypropylene glycol, 1.5 g of dibutyl tin oxide, 18 g of modified diol prepared by example one and 150 g of acetone were stirred and mixed uniformly, reacted at 60 °C for 2-4 h; 4 g of 1, 4-butanediol and 5 g of dimethylol propionic acid were added, and refluxed at 70 °C for 6 h; after the reaction was completed, 180 g of deionized water and 6 g of defoamer silicone defoamer were added, and high-speed shear emulsification was carried out for 60 min, then acetone was removed by distillation under reduced pressure to obtain a fluorine-containing polyurethane coating.

[0044] Comparative example one

[0045] Using the same quality of commercially available phosphorus flame retardant, replace the modified dihydric alcohol in Example 5, the remaining steps are the same as Example 5, to prepare the coating.

[0046] Comparative Example 2

[0047] Using commercially available fluorine-containing polyurethane coating.

[0048] The coating of Example 3, 4, 5, Comparative Example 1 and 2 is made into the corresponding shape according to different test standards, and the performance test is carried out as follows:

[0049] Adhesion is determined by using national standard GB / T 1720 “Paint film adhesion determination method”;

[0050] The acid and alkali resistance is determined by using national standard GB / T 1763 “Paint film chemical reagent resistance determination method”;

[0051] The heat resistance is determined by using national standard GB / T 1735 “Determination of heat resistance of color paint and varnish”;

[0052] The water resistance is determined by using national standard GB / T 1733 “Paint film water resistance determination method” before and after the sample is applied for 30 days;

[0053] The contact angle of the sample is determined by using DSC30 contact angle measuring instrument;

[0054] The burning time and mass loss of the sample are determined by using national standard GB 12441 “Decorative fireproof coating”, and the burning time and mass loss of Example 3, 4, 5 and Comparative Example 1 after being applied for 200 days are determined according to the standard;

[0055] The measured results are shown in the following table:

[0056]

[0057] As shown in the above table, the fluorine-containing polyurethane coating prepared by the embodiment of the present application has excellent corrosion resistance and water resistance due to the addition of modified dihydric alcohol, and the flame retardance, heat resistance and hydrophobicity are better than those of the comparative examples, and the performance is long and stable. In summary, the present application has important application value in the field of polyurethane coating technology.

[0058] In the description of the specification, the description of the reference terms “one embodiment”, “example”, “specific example” and the like 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 application. In the specification, the illustrative description 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.

[0059] The above merely illustrates and explains the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as the modifications or supplements do not deviate from the application or exceed the scope defined by the present claims, and should belong to the protection scope of the present application.

Claims

1. A process for the preparation of a fluorine-containing polyurethane coating, characterized in that, Comprising the following steps: In the reaction kettle, add preheated diphenyl methane diisocyanate, then pass nitrogen as protective gas, add polybutylene adipate glycol, polypropylene glycol, catalyst, modified diol and acetone, stir and mix uniformly, react for 2-4h at 50-60℃; add 1,4-butanediol and dimethylol propionic acid, reflux at 60-70℃ for 4-6h; after the reaction is completed, add deionized water and defoaming agent, high-speed shear emulsification for 30-60min, remove acetone by reduced pressure distillation, to obtain fluorine-containing polyurethane coating; Wherein, the modified diol is prepared by the following steps: S1, stir and mix uniformly melamine, diethyl phosphoacetic acid, dicyclohexyl carbodiimide and N,N-dimethyl formamide, then place in a 55℃ water bath, heat in water bath for 6h, after the reaction is completed, filter, distill under reduced pressure, wash, and vacuum dry to obtain intermediate 1; S2, mix and continuously stir hexafluoroglutaric chloride, aluminum chloride and N,N-dimethyl formamide until mixed uniformly, then drop 3-amino-1-propanol, after drop completion, react for 3h at 40℃, after the reaction is completed, filter, distill under reduced pressure to obtain intermediate 2; S3, mix and stir intermediate 2, intermediate 1 and N,N-dimethyl formamide uniformly, then add aluminum chloride, react for 6h at 55℃, after the reaction is completed, filter, rotary evaporate, column chromatography purification, rotary evaporate to obtain modified diol.

2. The method for preparing a fluorinated polyurethane coating according to claim 1, characterized in that, The amount ratio of melamine, diethyl phosphoacetic acid, dicyclohexyl carbodiimide, N,N-dimethyl formamide in step S1 is 14.3g:19.6g:20.6g:120mL.

3. The method for preparing a fluorinated polyurethane coating according to claim 1, characterized in that, The amount ratio of hexafluoroglutaric chloride, aluminum chloride, N,N-3-amino-1-propanol in step S2 is 28.7g:0.4g:100mL:7.5g.

4. The method for preparing a fluorinated polyurethane coating according to claim 1, characterized in that, The amount ratio of intermediate 2, intermediate 1, N,N-dimethyl formamide, aluminum chloride in step S3 is 67.3g:30.4g:200mL:0.9g.

5. The method for preparing a fluorinated polyurethane coating according to claim 1, characterized in that, Each raw material is as follows according to weight fraction: 30-50 parts of diphenyl methane diisocyanate, 20-30 parts of polybutylene adipate glycol, 25-35 parts of polypropylene glycol, 0.5-1.5 parts of catalyst, 6-18 parts of modified diol, 100-150 parts of acetone, 2-4 parts of 1,4-butanediol, 3-5 parts of dimethylol propionic acid, 120-180 parts of deionized water, 3-6 parts of defoaming agent.

6. The method for preparing a fluorinated polyurethane coating according to claim 1, characterized in that, The defoaming agent is silicone defoaming agent.

7. The method for preparing a fluorinated polyurethane coating according to claim 1, characterized in that, The catalyst is one of stannous octoate and dibutyl tin oxide.

Images