Novel self-emulsifying non-ionized water-dispersed saturated polyester dispersoid as well as preparation method and application thereof

Abstract

The invention provides a novel self-emulsifying nonionic water-dispersed saturated polyester dispersoid and a preparation method and application thereof, the novel self-emulsifying nonionic water-dispersed saturated polyester dispersoid comprises polyester and a water-containing solvent, and the polyester is obtained by esterifying first polyhydric alcohol, second polyhydric alcohol and polybasic acid; the first polyhydric alcohol comprises one or more of neopentyl glycol, trimethylolpropane, hexanediol, 1, 4-cyclohexanedimethanol (CHDM) and ethyl butyl propylene glycol (BEPD), and the second polyhydric alcohol comprises one or more of neopentyl glycol, trimethylolpropane, hexanediol, 1, 4-cyclohexanedimethanol (CHDM) and ethyl butyl propylene glycol (BEPD); the second polyhydric alcohol comprises polyethylene glycol; the weight part of the first polyhydric alcohol is 16 to 23 parts, the weight part of the second polyhydric alcohol is 2 to 10 parts, and the weight part of the binary acid is 28 to 35 parts. The water-dispersible saturated polyester dispersion provided by the invention has excellent storage stability, excellent water resistance and boiling water resistance, good compatibility and flexibility and low-foam property.

Description

Technical Field

[0001] This invention belongs to the field of waterborne coatings technology, and particularly relates to a novel self-emulsifying nonionic water-dispersible saturated polyester dispersion, its preparation method, and its application. Background Technology

[0002] Water-based coatings use water as a diluent, eliminating the flammable and explosive risks associated with organic solvents. This significantly improves the working environment in production workshops and construction sites, protecting the health of operators. They have garnered widespread attention and favor from coating R&D, manufacturing, and user companies.

[0003] Waterborne saturated polyesters are often combined with amino resins to form waterborne polyester-amino paints, primarily used in fields requiring high surface finish, durability, and environmental friendliness. Currently, the most common type on the market is the waterborne carboxylic acid anionic polyester, which is produced by introducing excess carboxyl groups (-COOH) onto the polyester molecular backbone and neutralizing them with organic amines (such as DMEA or ammonia) to form carboxylate anions (-COOH). - This allows for self-emulsifying dispersion in water.

[0004] However, waterborne carboxylic acid anionic polyesters have problems such as poor stability due to pH sensitivity during storage, and easy hydrolysis leading to demulsification and flocculation.

[0005] a. pH sensitivity (poor storage stability): The stability of the system is heavily dependent on the alkaline environment formed after amine neutralization (typically pH=7.5~9.0). If the amine volatilizes (during storage or baking), the pH drops, and the resin will change from an ionic state back to an acidic state, leading to demulsification, flocculation, and limited storage stability.

[0006] b. Poor water resistance: The neutralizing agent amine salt is a hydrophilic group. It cannot be completely volatilized during the curing process and will remain in the coating film, becoming a "water channel". This results in poor early water resistance and boiling water resistance of the coating film, and water spots and whitening are easy to occur.

[0007] c. More severe foaming: Anionic surfactants have higher surface activity and are more likely to stabilize bubbles, making defoaming difficult during construction.

[0008] d. Potential corrosion risk to metal substrates: Alkaline systems are corrosive to ordinary carbon steel equipment, requiring stainless steel or plastic linings.

[0009] e. Neutralize with ammonia. Strong odors, such as dimethylethanolamine and triethylamine, are highly irritating and toxic. They have a strong irritant smell on the skin, eyes and respiratory tract and may cause redness, swelling, pain, dizziness and nausea. Summary of the Invention

[0010] The application aims to provide a novel self-emulsifying nonionic water-dispersible saturated polyester dispersion, a preparation method and application thereof.

[0011] The application provides a novel self-emulsifying nonionic water-dispersible saturated polyester dispersion, which comprises a polyester and an aqueous solvent, and the polyester is obtained by esterification of a first polyol, a second polyol and a polybasic acid.

[0012] The first polyol comprises one or more of neopentyl glycol, trimethylolpropane, hexanediol, 1,4-cyclohexanedimethanol and ethyl butyl propylene glycol.

[0013] The second polyol comprises polyethylene glycol.

[0014] The first polyol is 16-23 parts by weight, the second polyol is 2-10 parts by weight, and the polybasic acid is 28-35 parts by weight.

[0015] Preferably, the aqueous solvent comprises an organic solvent and water, the organic solvent is 4-6 parts by weight, and the water is 40-60 parts by weight.

[0016] Preferably, the polybasic acid comprises one or more of isophthalic acid, hexahydrophthalic anhydride and tetrahydrophthalic anhydride.

[0017] Preferably, the molecular weight of the polyethylene glycol is 500-8000.

[0018] The application provides a preparation method of the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion as described above, comprising the following steps.

[0019] The first polyol, the second polyol and the polybasic acid are mixed and reacted under a protective atmosphere, the temperature is raised to 215-220 DEG C, the reaction is carried out until the acid value is less than 5 mgKOH / g, the temperature is lowered, the aqueous solvent is added, and the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion is obtained.

[0020] Preferably, after the first polyol, the second polyol and the polybasic acid are mixed, the temperature is first raised to 140-160 DEG C, and then the temperature is raised to 215-220 DEG C, and the reaction is carried out.

[0021] Preferably, after the reaction until the acid value is less than 5 mgKOH / g, the temperature is lowered to below 150 DEG C, the organic solvent is added, the temperature is continuously lowered to 65-70 DEG C, water is dispersed, and the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion is obtained.

[0022] Preferably, the organic solvent includes one or more of dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether and ethylene glycol propyl ether, and the mass of the organic solvent is 4-6% of the total mass of all raw materials;

[0023] The mass of the water is 40-60% of the total mass of all raw materials.

[0024] The present application provides a kind of water-based paint, including the following weight parts of components:

[0025] Water-based polyester resin: 70-80 parts, organic solvent: 1-5 parts, curing agent: 8-12 parts, defoaming agent: 0.05-0.5 parts, wetting agent: 0.1-0.5 parts, water: 1-10 parts;

[0026] The water-based polyester resin is the novel self-emulsifying nonionic water dispersion saturated polyester dispersion described above.

[0027] Preferably, the curing agent is amino resin; the defoaming agent includes one or more of silicone defoaming agent, polyether modified silicone defoaming agent and mineral oil defoaming agent; the wetting agent includes one or more of polyether siloxane copolymer, silicone modified wetting agent and acetylenic diol derivative; the organic solvent includes one or more of dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether and ethylene glycol propyl ether.

[0028] The present application provides a novel self-emulsifying nonionic water dispersion saturated polyester dispersion, including polyester and aqueous solvent, the polyester is obtained by esterification of first polyol, second polyol and polybasic acid; the first polyol includes one or more of neopentyl glycol, trimethylolpropane, hexanediol, 1,4-cyclohexane dimethanol (CHDM) and ethyl butyl propylene glycol (BEPD); the second polyol includes polyethylene glycol; the weight fraction of the first polyol is 16-23 parts, the weight fraction of the second polyol is 2-10 parts, and the weight fraction of the diacid is 28-35 parts. By introducing hydrophilic polyether segment (such as polyethylene glycol PEG) into the polyester molecule, water dispersion is realized by forming hydrogen bond between ether bond (-O-) in polyether segment and water molecules.

[0029] Compared with the prior art, the water dispersion saturated polyester dispersion in the present application has the following advantages:

[0030] a. Excellent storage stability (pH independent): due to the absence of ionic groups, its water dispersion stability is not affected by pH changes. It is very stable from acidic to alkaline conditions, has a longer storage period, and does not deteriorate due to amine volatilization.

[0031] b. Excellent water resistance and boiling water resistance: After film formation, the hydrophilic polyether segment is wrapped inside the coating film, which is much better than the carboxylic acid type. Because there is no hydrophilic amine salt, water molecules are difficult to penetrate.

[0032] c. Good compatibility and flexibility: The polyether segment gives the resin very good flexibility and internal plasticizing effect, and better compatibility with other water-based resins (such as acrylic, polyurethane). The coating film is flexible and not easy to crack.

[0033] d. Low foaming: Non-ionic surfactants have low foaming, and are not easy to produce stubborn bubbles during production and use. DETAILED DESCRIPTION

[0034] The present application provides a new self-emulsifying non-ionic water dispersion saturated polyester dispersion, comprising a polyester and an aqueous solvent, the polyester is obtained by esterification of a first polyol, a second polyol and a polybasic acid;

[0035] The first polyol includes one or more of neopentyl glycol, trimethylolpropane, hexanediol, 1,4-cyclohexane dimethanol and ethyl butyl propylene glycol;

[0036] The second polyol includes polyethylene glycol;

[0037] The weight fraction of the first polyol is 16-23 parts, the weight fraction of the second polyol is 2-10 parts, and the weight fraction of the diacid is 28-35 parts.

[0038] In the present application, the first polyol preferably includes one or more of neopentyl glycol, trimethylolpropane, hexanediol, 1,4-cyclohexane dimethanol and ethyl butyl propylene glycol; the weight fraction of the first polyol is preferably 16-23 parts, more preferably 18-22 parts, such as 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, preferably the above-mentioned any value as the upper limit or lower limit of the range value.

[0039] In the present application, the second polyol is preferably polyethylene glycol, the molecular weight of the polyethylene glycol is preferably 500-8000, such as PEG500, PEG1000, PEG2000, PEG4000, PEG8000, more preferably PEG2000; the weight fraction of the second polyol is preferably 2-10 parts, more preferably 4-6 parts, such as 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, preferably the above-mentioned any value as the upper limit or lower limit of the range value.

[0040] In the present application, the polybasic acid preferably comprises one or more of isophthalic acid, hexahydrophthalic anhydride (HHPA) and tetrahydrophthalic anhydride (THPA); the weight fraction of the dibasic acid is preferably 28-35 parts, more preferably 30-34 parts, such as 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, preferably a range value with any of the above values as the upper limit or lower limit.

[0041] In the present application, the aqueous solvent comprises an organic solvent and water, the organic solvent preferably comprises one or more of dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether and ethylene glycol propyl ether, the weight fraction of the organic solvent is preferably 4-6 parts, more preferably 5-6 parts; the weight fraction of the water is 40-60 parts, more preferably 45-55 parts.

[0042] The present application provides a preparation method of a novel self-emulsifying nonionic water-dispersible saturated polyester dispersion as described above, comprising the following steps:

[0043] In a protective atmosphere, the first polyol, the second polyol and the polybasic acid are mixed and reacted, and the temperature is raised to 215-220℃ until the acid value is <5 mgKOH / g, then the aqueous solvent is added to obtain the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion.

[0044] Preferably, in a protective atmosphere, after the first polyol, the second polyol and the polybasic acid are mixed, the temperature is first raised to 140-160℃, then raised to 215-220℃ for esterification, until the acid value is <5 mgKOH / g, then the organic solvent is added after the temperature is lowered to below 150℃, and the water is added after the temperature is further lowered to 65-70℃ for high-speed dispersion to obtain the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion.

[0045] In the present application, the types and amounts of the first polyol, the second polyol, the polybasic acid, the organic solvent and the water are the same as those described above, and will not be repeated here.

[0046] In the present application, the temperature rise to the esterification reaction temperature is divided into two stages, the first stage is to raise the temperature from room temperature to 140-160℃, more preferably 150-155℃, and the second stage is to raise the temperature from 140-160℃ to the esterification reaction temperature, the esterification reaction temperature is preferably 215-220℃, more preferably 216-218℃, and the temperature rise rate of the second stage is preferably 5-15℃ / h, more preferably 8-12℃ / h, most preferably 10-12℃ / h.

[0047] The present application also provides a water-based paint, comprising the following components by weight fraction:

[0048] Water-based polyester resin: 70-80 parts, organic solvent: 1-5 parts, curing agent: 8-12 parts, defoaming agent: 0.05-0.5 parts, wetting agent: 0.1-0.5 parts, water: 1-10 parts;

[0049] The water-based polyester resin is a new self-emulsifying nonionic water-dispersed saturated polyester dispersion as described above.

[0050] In the present application, the weight fraction of the water-based polyester resin is preferably 70-80 parts, more preferably 72-75 parts, such as 70 parts, 71 parts, 72 parts, 73 parts, 74 parts, 75 parts, 76 parts, 77 parts, 78 parts, 79 parts, 80 parts, preferably a range value with any of the above-mentioned values as the upper limit or lower limit.

[0051] In the present application, the organic solvent includes one or more of dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, and ethylene glycol propyl ether; the weight fraction of the organic solvent is preferably 1-5 parts, more preferably 2-4 parts, such as 1 part, 2 parts, 3 parts, 4 parts, 5 parts, preferably a range value with any of the above-mentioned values as the upper limit or lower limit.

[0052] In the present application, the curing agent is preferably an amino resin, more preferably 303 amino resin, and the weight fraction of the curing agent is preferably 8-12 parts, more preferably 9-11 parts, such as 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, preferably a range value with any of the above-mentioned values as the upper limit or lower limit.

[0053] In the present application, the defoaming agent preferably includes one or more of silicone defoaming agent, polyether-modified silicone defoaming agent, and mineral oil defoaming agent, and the weight fraction of the defoaming agent is preferably 0.05-0.5 parts, more preferably 0.1-0.4 parts, such as 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, preferably a range value with any of the above-mentioned values as the upper limit or lower limit.

[0054] In the present application, the wetting agent preferably includes one or more of polyether siloxane copolymer, silicone-modified wetting agent, and acetylenic glycol derivative, and the weight fraction of the wetting agent is preferably 0.1-0.5 parts, more preferably 0.2-0.4 parts, such as 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, preferably a range value with any of the above-mentioned values as the upper limit or lower limit.

[0055] In the present application, the water is preferably deionized water, and the weight fraction of the water is preferably 1-10 parts, more preferably 3-8 parts, such as 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, preferably a range value with any of the above values as the upper limit or lower limit.

[0056] Compared with the prior art, the water-dispersed saturated polyester dispersion in the present application has the following advantages:

[0057] a. Excellent storage stability (pH independent): due to the absence of ionic groups, the water dispersion stability is not affected by pH changes. It is very stable from acidic to alkaline conditions, has a longer storage period, and does not deteriorate due to amine volatilization.

[0058] b. Excellent water resistance and boiling water resistance: after film formation, the hydrophilic polyether segment is wrapped inside the coating film, and its water resistance is much better than that of the carboxylic acid type. Because there is no hydrophilic amine salt, water molecules are difficult to penetrate.

[0059] c. Good compatibility and flexibility: the polyether segment gives the resin good flexibility and internal plasticizing effect, and better compatibility with other water-based resins (such as acrylic, polyurethane). The coating film is flexible and not easy to crack.

[0060] d. Low foaming: non-ionic surfactants have low foaming, and are not easy to produce stubborn bubbles during production and use.

[0061] In order to further illustrate the present application, a new type of self-emulsifying non-ionic water-dispersible saturated polyester dispersion, its preparation method and application are described in detail below in combination with examples, but it should not be understood as limiting the scope of protection of the present application.

[0062] Examples 1-5

[0063] Referring to the raw material ratio in Table 1-Table 2, the materials TMP, NPG, HD, PEG, IPA are respectively put into the material, and the temperature is raised to 150°C under nitrogen protection, and the temperature is kept for 1 hour. The temperature is raised to 218°C±2°C at a rate of 10°C / h, and the acid value is less than 5mgKOH / g. The temperature is lowered to below 150°C, DPM is added, and the temperature is continuously lowered to 68°C±2°C. Water is dispersed at high speed, and the detection index is filtered and packaged.

[0064] Table 1 Raw materials of examples 1-5

[0065]

[0066] Table 2 Raw material ratio in examples 1-5

[0067]

[0068] Effect of polyethylene glycol molecular weight on resin storage stability

[0069] Centrifugal stability: centrifuge test, 3000R / min, every 0.5h to observe, according to the emulsion stratification evaluation. The results are shown in Table 3.

[0070] Table 3 Centrifugal stability

[0071]

[0072] Storage stability at room temperature and pressure: sealed and placed at room temperature and pressure, record the time of emulsion stratification, the results are shown in Table 4.

[0073] Table 4 Storage stability

[0074]

[0075] From the above table, it can be seen that under the condition of other conditions being basically the same, within a certain range, the storage stability is better with the increase of the molecular weight of polyethylene glycol. Because the molecular weight of polyethylene glycol is larger, the hydrophilic segment is longer, which can fully wrap the polyester segment microparticles, and the emulsification force of the microparticles is strong, so that the self-emulsifying water-based saturated polyester prepared has finer particle size and better storage stability.

[0076] Examples 6-10

[0077] According to the formulation in Table 5, water-based resin-amino baking paint coatings were prepared,

[0078] Table 5 Coating formulation of examples 6-10 (parts by weight)

[0079]

[0080] The water-based resin-amino baking paint was coated on the surface-treated tinplate with a wire bar, and placed at room temperature for 5 min, and baked at 180°C for 15 min; the dry film thickness was 14-16μm. The paint film was characterized for the following properties.

[0081] Determination of paint film adhesion

[0082] GB / T 9286-1998 (Cross-hatch test for pigmented and clear coatings) was used as the test standard. The standard provides a test method for evaluating the resistance of a coating to separation from a substrate by cutting the coating in a square grid pattern and penetrating to the substrate. The test results are divided into six grades, 5B being the best and 0B being the worst.

[0083] Determination of hardness

[0084] The hardness of different cross-linked films was determined by pencil hardness method, according to GB6739, using Chinese pencils with a hardness range of 2B-6H.

[0085] Paint film yellowing resistance determination

[0086] UV lamp method (lamp type yellowing resistance tester): according to the phenomenon that light color or white products are prone to color yellowing under long time irradiation of ultraviolet light, the sample surface color change is observed within a specified time under ultraviolet irradiation, and the degree of discoloration of the sample is determined, so as to determine the yellowing resistance of the material under ultraviolet radiation. The instrument JZ-300 is used for detection, and the total color difference is represented by ΔE. The larger the ΔE, the worse the yellowing resistance, and vice versa.

[0087] Paint film water resistance determination

[0088] Immersion test method: the immersion of the sample: add pure water or tap water (when specified by the customer) into a glass container, put 3 samples into it, and immerse 2 / 3 of the length of each sample in water, and stand at room temperature until the immersion time specified in the product standard ends. Inspection of the sample: take the sample out of the water, dry it with filter paper, immediately or after adjusting the time specified in the product standard, visually inspect it, and record whether there are phenomena such as loss of luster, discoloration, blistering, peeling, rusting, etc.

[0089] The test results are shown in Table 6.

[0090] Table 6 Performance data of paint film in examples 6-10

[0091]

[0092] As can be seen from Table 6, within a certain range, the adhesion gradually decreases with the increase of the molecular weight of polyethylene glycol; because polyethylene glycol is a linear structure soft segment, the larger the molecular weight, the longer the soft segment, and the fewer the intermolecular chemical crosslinking points, the adhesion decreases;

[0093] With the increase of the molecular weight of the emulsifier, the hardness gradually decreases; because polyethylene glycol is a linear structure soft segment, the larger the molecular weight, the longer the soft segment, and the lower the hardness;

[0094] With the increase of the molecular weight of the emulsifier, the paint film weather resistance is relatively stable. It shows that the emulsifier has little effect on the weather resistance of the paint film;

[0095] Within a certain range, with the increase of the molecular weight of polyethylene glycol, the water resistance of the paint film becomes worse; because polyethylene glycol is a hydrophilic raw material, the larger the molecular weight, the longer the hydrophilic segment, and the lower the water resistance.

[0096] Examples 11-16

[0097] The polyester dispersion was prepared according to the preparation method in Example 1, except that the type and amount of polyethylene glycol in Examples 11-16 were as shown in Table 7.

[0098] Table 7 Raw material ratio of examples 11~16 (weight fraction)

[0099]

[0100] Effect of polyethylene glycol content on resin storage stability

[0101] Centrifugal stability: detected by centrifuge, 3000R / min, every 0.5h, take out and observe, according to the emulsion stratification, the results are shown in Table 8.

[0102] Table 8 Centrifugal stability of examples 11~16

[0103]

[0104] Storage stability at room temperature and pressure: sealed and placed at room temperature and pressure, record the time of emulsion stratification, the results are shown in Table 9.

[0105] Table 9 Storage stability of examples 11~16

[0106]

[0107] From Table 8~9, it can be seen that within a certain range, with the increase of polyethylene glycol concentration, the particle size of the resin is finer, and the storage stability is better. But with the further increase of polyethylene glycol amount, the emulsion storage stability is worse.

[0108] When the emulsifier polyethylene glycol concentration is appropriate, with the increase of water amount, there is enough emulsifier to diffuse to the surface of the newly formed water droplets in time, which can wrap the small water droplets and form an interface film with certain tension. At this time, the repulsive force between water droplets is greater than the attractive force between water droplets, which ensures the constant size of water droplets. Further adding distilled water will make the distance between water droplets smaller, and the attractive force will increase sharply. When the water content reaches a certain critical value, the attractive force between water droplets is slightly greater than the repulsive force between water droplets. At this time, the surface tension of the system is very low, and the water droplets will fuse into a continuous phase under the action of shear, which will cause phase inversion and form O / W type emulsion. The emulsion obtained in this way has good stability and small size of dispersed phase particles. On the contrary, when the emulsifier concentration is too high, with the increase of emulsifier amount, the particle size of the obtained latex particles becomes smaller, the interfacial area increases, and the energy increases. According to the DLVO theory of colloidal stability, the total potential energy of the latex particles increases, and the chemical stability of the emulsion decreases.

[0109] Examples 17~22

[0110] According to the formula in Table 10, water-based resin-amino baking paint coating was prepared,

[0111] Table 10 Coating formula of examples 17~22 (weight fraction)

[0112]

[0113] The water-based resin-amino baking paint was coated on the surface-treated tinplate with a wire bar, and was placed at room temperature for 5 min and baked at 180°C for 15 min; the dry film thickness was 14-16 μm. The pencil hardness, yellowing resistance and water resistance of the paint film were characterized according to the methods described above. The results are shown in Table 11.

[0114] Table 11 Performance data of paint films in Examples 17-22

[0115]

[0116] As can be seen from Table 11, the hardness gradually decreases with the increase of the amount of polyethylene glycol. Since polyethylene glycol is a long-chain hydrophilic group soft segment, the more the amount, the lower the hardness. Conversely, the higher the hardness;

[0117] With the increase of the amount of polyethylene glycol, the water resistance of the paint film gradually decreases. Since polyethylene glycol is a long-chain hydrophilic group soft segment, the more the amount, the lower the hardness. Conversely, the higher the hardness;

[0118] With the increase of the amount of polyethylene glycol, the weather resistance of the paint film is relatively stable. It shows that the amount of polyethylene glycol has little effect on the weather resistance of the resin.

[0119] Example

[0120] The polyester dispersion was prepared according to the preparation method in Example 3. The difference is that the raw material ratio in Table 12 was used.

[0121] Table 12 Raw material ratio of Examples 23-26

[0122]

[0123] The water-based resin-amino baking paint was coated on the surface-treated tinplate with a wire bar, and was placed at room temperature for 5 min and baked at 180°C for 15 min; the dry film thickness was 14-16 μm. The pencil hardness, yellowing resistance and water resistance of the paint film were characterized according to the methods described above. The results are shown in Table 11.

[0124] Table 13 Performance data of paint films in Examples 23-26

[0125]

[0126] In summary, the waterborne saturated polyester dispersion prepared by the self-emulsifying method is prepared by introducing hydrophilic polar non-ionic polyethylene glycol into the polyester segment skeleton. These hydrophilic groups help to improve their solubility or dilution in water. The amount of polyethylene glycol is 2000, and the amount used is 4-6 parts by weight. The self-emulsifying waterborne saturated polyester dispersion prepared has the best comprehensive performance.

[0127] The above only describes the preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application. These improvements and refinements should also be considered within the scope of the present application.

Claims

1. A novel self-emulsifying nonionic water-dispersible saturated polyester dispersion, comprising a polyester and an aqueous solvent, wherein the polyester is obtained by esterification of a first polyol, a second polyol and a polybasic acid; the first polyol comprises one or more of neopentyl glycol, trimethylolpropane, hexanediol, 1,4-cyclohexanedimethanol and ethyl butyl propylene glycol; the second polyol comprises polyethylene glycol; the first polyol is in a weight fraction of 16-23 parts, the second polyol is in a weight fraction of 2-10 parts, and the polybasic acid is in a weight fraction of 28-35 parts.

2. The novel self-emulsifying non-ionic water-dispersible saturated polyester dispersion according to claim 1, characterized in that, the aqueous solvent comprises an organic solvent and water, wherein the organic solvent is in a weight fraction of 4-6 parts and the water is in a weight fraction of 40-60 parts.

3. The novel self-emulsifying non-ionic water-dispersible saturated polyester dispersion as claimed in claim 1, wherein, the polybasic acid comprises one or more of isophthalic acid, hexahydrophthalic anhydride and tetrahydrophthalic anhydride.

4. The novel self-emulsifying non-ionic water-dispersible saturated polyester dispersion as claimed in claim 1, wherein, the polyethylene glycol has a molecular weight of 500-8000. 5.A method for preparing the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion according to claim 1, comprising the following steps: mixing the first polyol, the second polyol and the polybasic acid in a protective atmosphere, and then reacting, heating to 215-220℃ and reacting until the acid value is less than 5 mgKOH / g, cooling, adding the aqueous solvent, and obtaining the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion.

6. A process for the preparation of novel self-emulsifying non-ionic water- dispersed saturated polyester dispersions according to claim 5, characterized in that, after mixing the first polyol, the second polyol and the polybasic acid, first heating to 140-160℃, keeping the temperature for 0.5-2 hours, then heating to 215-220℃, and reacting.

7. A process for the preparation of novel self-emulsifying non-ionic water- dispersible saturated polyester dispersions as claimed in claim 5, wherein, after the reaction until the acid value is less than 5 mgKOH / g, cooling to below 150℃, adding the organic solvent, continuing to cool to 65-70℃, adding water, and obtaining the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion.

8. A process for the preparation of novel self-emulsifying non-ionic water- dispersive saturated polyester dispersions according to claim 7, characterized in that, the organic solvent comprises one or more of dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether and ethylene glycol propyl ether, and the mass of the organic solvent is 4-6% of the total mass of all raw materials; the mass of the water is 40-60% of the total mass of all raw materials. 9.An aqueous coating, comprising the following components in parts by weight: aqueous polyester resin: 70-80 parts, organic solvent: 1-5 parts, curing agent: 8-12 parts, defoaming agent: 0.05-0.5 parts, wetting agent: 0.1-0.5 parts, and water: 1-10 parts; the aqueous polyester resin is the novel self-emulsifying nonionic water-dispersible saturated polyester dispersion according to any one of claims 1-4.

10. The aqueous coating of claim 8, wherein, the curing agent is an amino resin;the defoaming agent comprises one or more of silicone defoaming agent, polyether-modified silicone defoaming agent and mineral oil defoaming agent;the wetting agent comprises one or more of polyether siloxane copolymer, silicone-modified wetting agent and acetylenic diol derivative;and the organic solvent comprises one or more of dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether and ethylene glycol propyl ether.

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