Organic silicon modified waterborne polyester resin suitable for coiled material coating and preparation method of organic silicon modified waterborne polyester resin

Abstract

According to the organic silicon modified water-based polyester resin suitable for the coiled material coating and the preparation method of the organic silicon modified water-based polyester resin, a siloxane chain segment is introduced into the water-based polyester resin through methyltriethoxysilane for organic silicon modification, and a modified polymer coating is endowed with excellent water resistance; according to the polyester resin, cyclohexanediol and 2, 2-difluoro-1, 3-propylene glycol in a specific ratio are taken as dihydric alcohol, so that the heat resistance and the mechanical property of the polyester resin can be improved, C-F bonds are introduced into a polymer molecular chain by 2, 2-difluoro-1, 3-propylene glycol, and the 2, 2-difluoro-1, 3-propylene glycol is bonded with ester groups and hydroxyl groups in the polyester molecular chain, so that the heat stability of the polyester resin can be improved; meanwhile, the introduction of a C-F bond further reduces the surface energy of the polyester resin, so that the coating shows higher hydrophobicity. The water-based polyester resin prepared by the invention is concentrated in particle size distribution, and can be stably stored after being prepared into water-based paint.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic resins, and in particular relates to an organosilicon-modified waterborne polyester resin suitable for coil coatings and a preparation method thereof. Background Art

[0002] Polyester resin is a polymer compound formed by polycondensation of diols or dibasic acids or polyols and polyacids. When used in coatings, polyester resin coatings have excellent physical and chemical properties, such as high hardness, high gloss, good fullness, good flexibility, good abrasion resistance, good gloss and color retention, etc. These properties make polyester resin coatings have broad application prospects in the field of coil coatings. Compared with traditional solvent-based coatings, water-based coatings have lower volatile organic compounds (VOCs) emissions and are more conducive to environmental protection and human health. Therefore, it is very necessary to develop water-based polyester coatings with excellent comprehensive performance for coil coatings.

[0003] Chinese invention patent application CN107652854A discloses a UV system aluminum coil coating, wherein the weight percentage of each component of the aluminum coil coating is: 10-15% pentaerythritol tetraacrylate, 25-35% trimethylolpropane triacrylate, 10-16% E-20 epoxy resin dimethacrylate, 20-30% diethylene glycol diacrylate, 15-25% methyl propylene glycol diacrylate, 1-3% photoinitiator 184, 2-10% various color pigments, 10-15% precipitated barium sulfate, 1-3% polyethylene wax powder, 2-4% wetting dispersant, 1-2% defoamer, 2-5% leveling agent, 0.5-1.5% polymerization inhibitor. The coating has the characteristics of energy saving and environmental protection, but has poor heat resistance and adhesion to metal.

[0004] Chinese invention patent application CN111073471A discloses a coil coating for a velvet glittering surface plate for aluminum coils, which includes the following components and their weight percentages: 5-10% environmentally friendly solvent, 0.5-1% dispersant, 0.5-1% catalyst, 5-10% amino resin, 0.3-0.5% defoamer, 0.5%-1.0% adhesion agent, 0.3-3% leveling agent, 1-3% directional arrangement assistant, 0.5-1% antistatic assistant, 10-20% nano-level pearlescent paste, 50-70% polyester resin, and 3-6% silane polymer powder. The coil coating of the invention uses an environmentally friendly solvent, has the advantages of good surface visual effect and a velvet glittering surface plate for aluminum coils with a smooth feel, but the coating is not resistant to high temperatures.

[0005] Although the coil coatings in the above-mentioned prior art all use polyester resins and focus on the environmental protection of the coatings, the comprehensive performance of the coatings is not ideal.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure. Summary of the invention

[0007] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a silicone-modified waterborne polyester resin suitable for coil coatings.

[0008] The purpose of the present invention is achieved through the following technical solutions: A method for preparing a silicone-modified waterborne polyester resin suitable for coil coatings, the method comprising the following steps: (1) In a nitrogen or rare gas atmosphere, 30-40 parts by weight of diol, 40-60 parts by weight of aromatic dibasic acid, 3-5 parts by weight of polyol branching agent and 0.1-0.5 parts by weight of catalyst are subjected to esterification reaction at 200-240° C. for 4-6 hours, and then 10-20 parts by weight of anhydride capping agent is added to carry out capping reaction; (2) After cooling the reaction system to 85-95°C, methyltriethoxysilane (MTES) was added to the reaction system and stirred, and then distilled water was added to keep the temperature for 2-3 hours to carry out organosilicon modification; (3) After cooling the reaction system to 50-60° C., 20-25 parts by weight of a hydrophilic solvent is added to the reaction system and mixed evenly, followed by adding N,N-dimethylethanolamine to adjust the pH to 7-8, and finally adding distilled water to adjust the solid content to 45-65% to obtain the silicone-modified waterborne polyester resin suitable for coil coating.

[0009] Preferably, the diol is composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of (8-10):1.

[0010] Preferably, the aromatic dibasic acid is at least one of phthalic acid, isophthalic acid and terephthalic acid.

[0011] Preferably, the polyol branching agent is any one of dimethylolpropionic acid, trimethylolpropane and trimethylolethane.

[0012] Preferably, the catalyst is any one of tetrabutyl titanate, tetraisopropyl titanate and tetraisobutyl titanate.

[0013] Preferably, the acid anhydride capping agent is 1,2-cyclohexanedicarboxylic anhydride or maleic anhydride.

[0014] Preferably, the amount of methyltriethoxysilane added in step (2) is 5-12% of the total mass of the diol and the aromatic dibasic acid.

[0015] Preferably, the amount of distilled water added in step (2) is 5-10 parts by weight.

[0016] Preferably, the hydrophilic solvent is one of ethylene glycol monobutyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, and diethylene glycol butyl ether, or a mixture of any proportions. The addition of a hydrophilic solvent can help the resin to be better dissolved and dispersed in water, thereby improving the water solubility and dispersibility of the resin and improving the storage stability of the resin; in addition, it can reduce the viscosity of the water-based polyester resin system, making the resin easier to process and apply.

[0017] The organosilicon-modified waterborne polyester resin prepared by the method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coatings.

[0018] Compared with the prior art, the present invention has the following advantages and effects: (1) The present invention introduces siloxane segments into water-based polyester resin by methyltriethoxysilane to carry out organosilicon modification. Organosilicon has a unique structure and has both organic groups and inorganic groups. Its low surface energy can be enriched on the film surface during coating film formation to form a stable protective layer rich in Si-O-Si chains, so that the hydrophobicity of the coating film is increased, the contact angle is increased, and the water absorption rate is reduced, thereby giving the modified polymer coating excellent water resistance; at the same time, the Si-O bond with larger bond energy introduced by organosilicon modification has higher thermal stability than the CC bond or CO bond in the polyester resin, and the silicon atom and oxygen atom in the Si-O bond can form a d-pπ bond. This bond structure further increases the thermal stability and chemical resistance of the polyester resin, and at the same time can avoid the problem of poor compatibility between silicone resin and water-based polyester.

[0019] (2) The present invention uses cyclohexanediol and 2,2-difluoro-1,3-propanediol in a specific ratio as diols to carry out esterification reaction with aromatic dibasic acid and branching agent. Both cyclohexanediol and aromatic dibasic acid have rigid ring structure, which is beneficial to increase the heat resistance and mechanical properties of polyester resin. 2,2-difluoro-1,3-propanediol introduces CF bond into the polymer molecular chain, which forms bonds with ester group and hydroxyl group in the polyester molecular chain to increase the thermal stability of polyester resin. At the same time, the introduction of CF bond further reduces the surface energy of polyester resin, so that the coating exhibits higher hydrophobicity.

[0020] (3) The particle size distribution of the water-based polyester resin prepared by the present invention is concentrated, and the introduction of silicone segments and fluorine atoms is beneficial to enhancing the interaction between the polyester resin and the surface molecules of the substrate, so that the water-based coating can be stably stored after being prepared.

[0021] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. DETAILED DESCRIPTION

[0022] The embodiments of the present invention will be clearly and completely described below in conjunction with the examples, and the described examples are only some examples of the present invention, rather than all examples. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the examples in the present invention, all other examples obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0023] The reagents or instruments used in the present invention, if the manufacturer is not specified, are all conventional products that can be purchased from the market. For process parameters not specifically specified, conventional techniques can be used.

[0024] Example 1

[0025] This embodiment provides a method for preparing a silicone-modified waterborne polyester resin suitable for coil coating, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 9:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After cooling the reaction system to 85° C., 5 parts by weight of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by weight of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the silicone-modified waterborne polyester resin suitable for coil coatings.

[0026] After testing, the organosilicon-modified waterborne polyester resin prepared in this embodiment has a Tg of 316° C., a viscosity of 445 mPa·s, an average particle size of 39.97 nm, a PDI of 0.306, and a light blue and transparent appearance.

[0027] Example 2 This embodiment provides a method for preparing a silicone-modified waterborne polyester resin suitable for coil coating, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 9:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After cooling the reaction system to 85° C., 8 parts by weight of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by weight of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the silicone-modified waterborne polyester resin suitable for coil coatings.

[0028] After testing, the organosilicon-modified waterborne polyester resin prepared in this embodiment has a Tg of 325° C., a viscosity of 404 mPa·s, an average particle size of 44.64 nm, a PDI of 0.339, and a light blue and transparent appearance.

[0029] Example 3

[0030] This embodiment provides a method for preparing a silicone-modified waterborne polyester resin suitable for coil coating, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 9:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After cooling the reaction system to 85° C., 10 parts by weight of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by weight of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the silicone-modified waterborne polyester resin suitable for coil coatings.

[0031] After testing, the organosilicon-modified waterborne polyester resin prepared in this embodiment has a Tg of 331° C., a viscosity of 311 mPa·s, an average particle size of 48.65 nm, a PDI of 0.195, and a light blue and transparent appearance.

[0032] Example 4

[0033] This embodiment provides a method for preparing a silicone-modified waterborne polyester resin suitable for coil coating, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 9:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After cooling the reaction system to 85° C., 12 parts by weight of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by weight of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the silicone-modified waterborne polyester resin suitable for coil coatings.

[0034] After testing, the organosilicon-modified waterborne polyester resin prepared in this embodiment has a Tg of 338° C., a viscosity of 324 mPa·s, an average particle size of 57.86 nm, a PDI of 0.352, and a light blue and transparent appearance.

[0035] Example 5

[0036] This embodiment provides a method for preparing a silicone-modified waterborne polyester resin suitable for coil coating, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 8:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After cooling the reaction system to 85° C., 10 parts by weight of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by weight of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the silicone-modified waterborne polyester resin suitable for coil coatings.

[0037] After testing, the organosilicon-modified waterborne polyester resin prepared in this embodiment has a Tg of 327° C., a viscosity of 368 mPa·s, an average particle size of 50.25 nm, a PDI of 0.258, and a light blue and transparent appearance.

[0038] Comparative Example 1

[0039] This comparative example provides a method for preparing an aqueous polyester resin, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 9:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the water-based polyester resin.

[0040] That is, the difference between this comparative example and Example 3 is that methyltriethoxysilane is not added to modify the polyester resin.

[0041] After testing, the water-based polyester resin prepared in this comparative example has a Tg of 269° C., a viscosity of 1438 mPa·s, an average particle size of 13.93 nm, a PDI of 0.568, and a light yellow and transparent appearance.

[0042] Comparative Example 2

[0043] This comparative example provides a method for preparing an aqueous polyester resin, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 9:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After the reaction system was cooled to 85° C., 3 parts by mass of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by mass of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the water-based polyester resin.

[0044] That is, the difference between this comparative example and Example 3 is that the amount of methyltriethoxysilane used is 3% of the total mass of the diol and the aromatic dibasic acid.

[0045] After testing, the water-based polyester resin prepared in this comparative example has a Tg of 303° C., a viscosity of 832 mPa·s, an average particle size of 26.34 nm, a PDI of 0.397, and a light yellow and transparent appearance.

[0046] Comparative Example 3

[0047] This comparative example provides a method for preparing an aqueous polyester resin, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by mass of a diol (composed of cyclohexanediol and 2,2-difluoro-1,3-propanediol in a molar ratio of 9:1), 60 parts by mass of an aromatic dibasic acid (phthalic acid), 5 parts by mass of a polyol branching agent (dimethylol propionic acid) and 0.5 parts by mass of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 hours, and then 10 parts by mass of an anhydride capping agent (maleic anhydride) was added for a capping reaction; (2) After cooling the reaction system to 85° C., 15 parts by weight of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by weight of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the water-based polyester resin.

[0048] That is, the difference between this comparative example and Example 3 is that the amount of methyltriethoxysilane used is 15% of the total mass of the diol and the aromatic dibasic acid.

[0049] The water-based polyester resin prepared in this comparative example has a light blue appearance and has precipitation at the bottom.

[0050] Comparative Example 4

[0051] This comparative example provides a method for preparing an aqueous polyester resin, comprising the following steps: (1) In a nitrogen atmosphere, 40 parts by weight of a diol (cyclohexanediol), 60 parts by weight of an aromatic dibasic acid (phthalic acid), 5 parts by weight of a polyol branching agent (dimethylolpropionic acid) and 0.5 parts by weight of a catalyst (tetrabutyl titanate) were subjected to an esterification reaction at 220°C for 6 h, and then 10 parts by weight of an anhydride capping agent (maleic anhydride) was added for capping reaction; (2) After cooling the reaction system to 85° C., 10 parts by weight of methyltriethoxysilane was added to the reaction system and stirred, and then 10 parts by weight of distilled water was added dropwise and the reaction was kept warm for 3 hours to perform organosilicon modification; (3) After the reaction system is cooled to 60° C., 20 parts by weight of a hydrophilic solvent (ethylene glycol monobutyl ether) is added to the reaction system and mixed evenly, followed by addition of N,N-dimethylethanolamine to adjust the pH to 7, and finally, distilled water is added to adjust the solid content to 60% to obtain the water-based polyester resin.

[0052] That is, the difference between this comparative example and Example 3 is that the diol does not contain 2,2-difluoro-1,3-propanediol.

[0053] After testing, the water-based polyester resin prepared in this comparative example has a Tg of 295° C., a viscosity of 524 mPa·s, an average particle size of 37.22 nm, a PDI of 0.384, and a light blue and transparent appearance.

[0054] Performance Testing

[0055] In order to further demonstrate the beneficial effects of the present invention, the water-based polyester resins prepared in the above examples and comparative examples were made into coatings according to the following method for performance testing: Weigh 40 parts by weight of water-based polyester resin, 10 parts by weight of titanium dioxide, 0.2 parts by weight of BYK-024 defoamer, 0.2 parts by weight of BYK-154 dispersant, and 30 parts by weight of deionized water; add titanium dioxide and dispersant into deionized water, and stir at 600 rpm / min for 10 min; then add water-based polyester resin and defoamer, and stir at 800 rpm / min for 30 min; then add 5 parts by weight of amino resin curing agent and mix well to obtain a coating.

[0056] 1. Storage stability test The storage stability of the coating was tested with reference to GB / T 6753.3-1986 “Test method for storage stability of coatings”. The test results are shown in Table 1.

[0057] The coating was coated on several surface-treated tinplates using a film applicator. The thickness of the wet film was 100 μm. The coating was allowed to stand at room temperature until the surface was dry and then placed in an oven for pre-baking at 80°C for 1 hour. The temperature was then raised to 100°C and dried for 30 minutes. Finally, the coating was cured at 140°C for 30 minutes to obtain test specimens, which were subjected to the following performance tests.

[0058] 2. Hydrophobicity test The water absorption rate of the sample was tested according to "Determination of Water Absorption of Plastics (GB / T 1034-2008) (ISO 62:2008)", and the water contact angle of the coating was measured with a surface contact angle meter to test the hydrophobicity of the coating. The test results are shown in Table 1.

[0059] 3. Water resistance test The water resistance of the sample was tested with reference to GB / T 1733-1993 Determination of water resistance of paint film. The test results are shown in Table 1.

[0060] 4. Adhesion, hardness and chemical resistance tests Referring to GB / T 13448-2019 Test Methods for Color Coated Steel Sheets and Steel Strips, the sample was subjected to a cross-cutting test, a pencil hardness test, an acid and alkali resistance test, and an organic solvent (ethanol) resistance test to test the adhesion, hardness, and chemical resistance of the coating. The test results are shown in Table 2.

[0061] 5. Impact resistance test The impact resistance of the coating was tested according to the standard of GB / T 1732-2020. The test results are shown in Table 2.

[0062] Table 1 Waterborne polyester resin coating performance test results 1

[0063] Table 2 Waterborne polyester resin coating performance test results II

[0064] It can be seen from the test results of Example 3 and Comparative Example 1 that the present invention introduces siloxane segments into the water-based polyester resin through methyltriethoxysilane for organosilicon modification, so that the hydrophobicity of the coating film is increased, the contact angle is increased, and the water absorption rate is reduced, thereby giving the modified polymer coating excellent water resistance; at the same time, the organosilicon modification further increases the thermal stability and chemical resistance of the polyester resin.

[0065] It can be seen from the test results of Example 3 and Comparative Example 2 that when the amount of methyltriethoxysilane is too low, the comprehensive performance of the coating is insufficient; it can be seen from the test results of Example 3 and Comparative Example 3 that when the amount of methyltriethoxysilane is too high, the polyester resin particle size is too large to form a uniformly dispersed clear liquid, the adhesion of the coating is significantly reduced and cannot meet the requirements of the coil coating.

[0066] It can be seen from the test results of Example 3 and Comparative Example 4 that when 2,2-difluoro-1,3-propanediol is not introduced in the process of synthesizing the polyester resin, the water resistance and mechanical properties of the coating are reduced.

[0067] Based on the above test results, it can be seen that after the silicone-modified water-based polyester resin prepared by the present invention is made into a coating, the coating has excellent hydrophobicity, water resistance, chemical resistance and impact resistance, and is suitable for preparing water-based coil coatings.

[0068] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a silicone-modified waterborne polyester resin suitable for coil coatings, characterized in that: The method comprises the following steps: (1) In a nitrogen or rare gas atmosphere, 30-40 parts by weight of diol, 40-60 parts by weight of aromatic dibasic acid, 3-5 parts by weight of polyol branching agent and 0.1-0.5 parts by weight of catalyst are subjected to esterification reaction at 200-240° C. for 4-6 hours, and then 10-20 parts by weight of anhydride capping agent is added to carry out capping reaction; (2) After cooling the reaction system to 85-95°C, methyltriethoxysilane was added to the reaction system and stirred, and then distilled water was added to keep the temperature for 2-3 hours to carry out organosilicon modification; (3) After cooling the reaction system to 50-60° C., 20-25 parts by weight of a hydrophilic solvent is added to the reaction system and mixed evenly, followed by adding N,N-dimethylethanolamine to adjust the pH to 7-8, and finally adding distilled water to adjust the solid content to 45-65% to obtain the silicone-modified waterborne polyester resin suitable for coil coating.

2. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The diol is composed of cyclohexanediol and 2,2-difluoro-1,3-propylene glycol in a molar ratio of (8-10):

1.

3. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The aromatic dibasic acid is at least one of phthalic acid, isophthalic acid and terephthalic acid.

4. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The polyol branching agent is any one of dimethylol propionic acid, trimethylol propane and trimethylol ethane.

5. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The catalyst is any one of tetrabutyl titanate, tetraisopropyl titanate and tetraisobutyl titanate.

6. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The acid anhydride end-capping agent is 1,2-cyclohexanedicarboxylic anhydride or maleic anhydride.

7. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The amount of methyltriethoxysilane added in step (2) is 5-12% of the total mass of the diol and the aromatic dibasic acid.

8. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The amount of distilled water added in step (2) is 5-10 parts by weight.

9. The method for preparing the organosilicon-modified waterborne polyester resin suitable for coil coating according to claim 1, characterized in that: The hydrophilic solvent is one of ethylene glycol monobutyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, and diethylene glycol butyl ether, or a mixture of any proportions of the above-mentioned solvents.

10. The organosilicon-modified waterborne polyester resin prepared by the method for preparing an organosilicon-modified waterborne polyester resin suitable for coil coating according to any one of claims 1 to 9.

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