Water-based modified polyester dispersion, coating and preparation method of water-based modified polyester dispersion

Abstract

The invention discloses a water-based modified polyester dispersion, a coating and a preparation method of the water-based modified polyester dispersion. The water-based modified polyester dispersion is prepared from the following raw material components: polyether monoamine, epoxy resin, dimethylolbutyric acid and / or dimethylolpropionic acid, tetrabutylammonium bromide, polybasic acid, polyhydric alcohol, dicarboxylic anhydride and an esterification catalyst. The water-based modified polyester dispersion prepared by the invention has zero volatile component content and good storage stability, and the obtained water-based paint has good boiling resistance, impact resistance, T-bend resistance, acid and alkali resistance and excellent comprehensive performance.

Description

Technical Field

[0001] The invention relates to the field of waterborne polyester, in particular to a waterborne modified polyester dispersion and a preparation method thereof. Background Art

[0002] Coil coating is a special coating used to coat the surface of steel plates, aluminum plates and other substrates to make pre-coated coils. According to statistics, the most widely used coil coating is the polyester system, accounting for about 60%, and the rest are PVC plastisol, PVDF, silicone modified polyester, etc. The paint film obtained by cross-linking and curing polyester resin with amino resin or blocked isocyanate has high hardness, good flexibility and is the most widely used. In recent years, with the increasingly stringent environmental protection policies, the development of UV-curable coil coatings and water-based coil coatings is in the ascendant.

[0003] However, the current water-based polyester technology mostly introduces ionic groups into the polyester molecular chain to make it hydrophilic, and most of them contain 20-40% alcohol ether cosolvents or a certain amount of amine neutralizers (dimethylethanolamine, etc.), and the VOC (volatile organic compounds) is still very high. Summary of the invention

[0004] In view of the defects of the prior art, the object of the present invention is to provide a modified waterborne polyester dispersion and coating and a preparation method thereof, wherein the modified waterborne polyester dispersion has excellent performance and contains no volatile matter at all.

[0005] The technical solution of the present invention is as follows:

[0006] A water-based modified polyester dispersion comprises the following raw material components: polyether monoamine, epoxy resin, dimethylolbutyric acid and / or dimethylolpropionic acid, tetrabutylammonium bromide, polyacid, polyol, dibasic acid anhydride and esterification catalyst.

[0007] Preferably, the molar ratio of the hydroxyl groups in the polyol to the carboxyl groups in the polyacid is 1.05-1.25:1, the molar amount of the dibasic acid anhydride is 40-80% of the molar amount of excess alcohol hydroxyl groups, and the molar amount of excess alcohol hydroxyl groups is equal to the molar amount of the hydroxyl groups in the polyol minus the molar amount of the carboxyl groups in the polyacid.

[0008] Preferably, the molar ratio of the polyether monoamine, dimethylolbutyric acid and / or dimethylolpropionic acid, epoxy resin and dibasic acid anhydride is 1:1:1:1-1.15.

[0009] Preferably, the mass of the tetrabutylammonium bromide is 0.1-0.5% of the total mass of the raw material components.

[0010] Preferably, the mass of the esterification catalyst is 0.1-0.5% of the total mass of the polyacid and the polyol.

[0011] Preferably, the aqueous modified polyester dispersion further comprises an antioxidant, and the mass of the antioxidant is 0.1-0.5% of the total mass of the polyacid and the polyol.

[0012] Preferably, the antioxidant is selected from hypophosphorous acid and / or triphenyl phosphite.

[0013] Preferably, the polyol is selected from one or more of neopentyl glycol, trimethylolpropane, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 2-ethyl-1,3-hexanediol, hexanediol, and 2-butyl-2-ethyl-1,3-propanediol.

[0014] Preferably, the polyacid is selected from one or more of adipic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride.

[0015] Preferably, the catalyst is selected from one or more of dibutyltin oxide, dibutyltin dilaurate, and tetraisopropyl titanate.

[0016] Preferably, the dibasic acid anhydride is selected from one or more of phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride and hexahydrophthalic anhydride.

[0017] Preferably, the polyether monoamine has an amine value of 0.30-1.08 and / or a molecular weight of 1000-3000.

[0018] Preferably, the epoxy resin is bisphenol A epoxy resin and / or bisphenol F epoxy resin with an epoxy equivalent of 450 to 1700.

[0019] The present invention further provides a method for preparing the above-mentioned aqueous modified polyester dispersion, which comprises:

[0020] (1) reacting the polyether monoamine and the dimethylolbutyric acid and / or dimethylolpropionic acid at 150-200° C. until no water is produced and removing the residual solvent in vacuo, adding the epoxy resin and reacting at 120-130° C. to obtain a monoepoxy hydrophilic polymer;

[0021] (2) The polyacid and polyol are heated to 145-155° C. under inert atmosphere protection, the esterification catalyst is added, the temperature is raised to 180-220° C. and the reaction is continued until the acid value reaches 2-10 mgKOH / g, the temperature is lowered to 140-160° C. and the dibasic acid anhydride is added, the reaction is continued for 1-1.5 hours, the monoepoxy hydrophilic polymer and tetrabutylammonium bromide are added, the reaction is continued at 140-160° C. until the acid value no longer decreases, and a modified polyester resin is obtained;

[0022] (3) adding the modified polyester resin into deionized water at 70-90° C. to dissolve the modified polyester resin, thereby obtaining the aqueous modified polyester dispersion.

[0023] Preferably, step (2) further comprises heating the antioxidant, the polyacid and the polyol to 145-155° C. under the protection of an inert atmosphere.

[0024] According to the above water-based modified polyester dispersion, the present invention can further obtain a zero-volatile water-based coating, which has excellent environmental protection performance and is resistant to boiling, impact, T-bending, acid and alkali, and butanone wiping.

[0025] In the water-based modified polyester dispersion and the preparation method thereof, a monoepoxy hydrophilic polymer with excellent hydrophilicity can be obtained by reacting the primary amino group of the polyether monoamine with the carboxyl group of dimethylolbutyric acid and / or dimethylolpropionic acid and by reacting the secondary amino group with the epoxy resin; further, a hydroxyl-terminated polyester resin can be synthesized by polyacids and polyols, a dibasic acid anhydride can react with a hydroxyl group to obtain a carboxyl-terminated polyester, and finally the carboxyl-terminated polyester resin is grafted with a monoepoxy hydrophilic polymer, and hydrophilization is achieved by the nonionic hydrophilic chain segment on the monoepoxy hydrophilic polymer. No cosolvent and amine neutralizer need to be added during the synthesis, and a completely volatile-free preparation is achieved. Meanwhile, in each raw material component, the epoxy resin, dimethylolbutyric acid and / or dimethylolpropionic acid can introduce more highly active hydroxyl groups, thereby increasing the crosslinking density of the material after the reaction with the amino resin, and increasing its hardness and durability, while the polyether chain segment of the polyether monoamine can provide flexibility, achieving a balance between hardness and toughness, and obtaining a water-based modified polyester dispersion with excellent performance and stable storage. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0027] Example 1

[0028] The aqueous modified polyester dispersion was prepared by the following steps:

[0029] (1) 83.4 g of a polyether monoamine with a molecular weight of 1000 and 12.4 g of dimethylolbutyric acid were subjected to reflux reaction at 180-190° C., and after the reaction was stopped until water was no longer produced, the reflux solvent was removed by vacuum, and then 32.7 g of epoxy resin E51 was added and reacted at 120-130° C. until the active hydrogen was completely reacted, thereby obtaining a monoepoxy hydrophilic polymer B;

[0030] (2) 40 g of adipic acid, 70 g of isophthalic acid, 71.3 g of 3-methyl-1,5-pentanediol, 37.3 g of 1,4-cyclohexanedimethanol and 0.5 g of triphenyl phosphite are heated to 150° C. under nitrogen protection, 0.4 g of dibutyltin oxide is added, and the temperature is continued to rise to 195-205° C. to react until the acid value reaches 2-5 mgKOH / g, the temperature is lowered to 140-150° C., 12.4 g of phthalic anhydride is added, the reaction is continued for 1.5 h, polymer B and 0.2 g of tetrabutylammonium bromide are added for end-capping reaction, the reaction is continued at 150-160° C. until the acid value no longer decreases, and the temperature is lowered to obtain modified polyester resin A;

[0031] (3) 539 g of deionized water was heated to 75-85° C., and the modified polyester resin A was added while being stirred to dissolve, thereby obtaining a zero-VOC aqueous modified polyester dispersion.

[0032] Example 2

[0033] The aqueous modified polyester dispersion was prepared by the following steps:

[0034] (1) 65.4 g of a polyether monoamine having a molecular weight of 2000 and 4.4 g of dimethylol propionic acid are subjected to reflux reaction at 190-200° C., and after the reaction stops producing water, the reflux solvent is removed by vacuum, and then 14.9 g of epoxy resin E44 is added, and the reaction is continued at 120-130° C. until the active hydrogen reacts completely, thereby obtaining a monoepoxy hydrophilic polymer B;

[0035] (2) 40 g of hexahydrophthalic anhydride, 70 g of isophthalic acid, 61.1 g of 2-butyl-2-ethyl-1,3-propanediol, 45.1 g of 3-methyl-1,5-pentanediol and 0.3 g of triphenyl phosphite are heated to 150° C. under nitrogen protection, 0.4 g of dibutyltin oxide is added, and the temperature is continued to rise to 195-205° C., and the reaction is carried out until the acid value reaches 2-5 mgKOH / g, the temperature is lowered to 150-160° C., 3.2 g of maleic anhydride is added, and the reaction is carried out for 1 h, and then the polymer B obtained in S1 and 0.2 g of tetrabutylammonium bromide are added for end-capping reaction, the reaction is carried out at 150-160° C. until the acid value no longer decreases, and the temperature is lowered to obtain a modified polyester resin A;

[0036] (3) 456 g of deionized water was heated to 75-85° C., and the modified polyester resin A was added while being stirred to dissolve, thereby obtaining a zero-VOC aqueous modified polyester dispersion.

[0037] Example 3

[0038] The aqueous modified polyester dispersion was prepared by the following steps:

[0039] (1) 15.8 g of a polyether monoamine with a molecular weight of 1000, 47.5 g of a polyether monoamine with a molecular weight of 3000 and 4.7 g of dimethylolbutyric acid are subjected to reflux reaction at 180-190° C., and after the reaction is continued until no water is produced, the reflux solvent is removed by vacuum, and then 31.6 g of epoxy resin E20 is added, and the reaction is continued at 120-130° C. until the active hydrogen reacts completely, thereby obtaining a monoepoxy hydrophilic polymer B;

[0040] (2) 50 g of adipic acid, 60 g of isophthalic acid, 39.9 g of neopentyl glycol, 90.6 g of 3-methyl-1,5-pentanediol and 0.3 g of triphenyl phosphite are heated to 150° C. under nitrogen protection, 0.5 g of dibutyltin oxide is added, and the temperature is continued to rise to 210-220° C., and the reaction is carried out until the acid value reaches 4-7 mgKOH / g, the temperature is lowered to 140-150° C., 3.1 g of maleic anhydride is added, and the reaction is carried out for 1.5 h, and then polymer B and 0.2 g of tetrabutylammonium bromide are added for end-capping reaction, and the reaction is carried out at 145-155° C. until the acid value no longer decreases, and the temperature is lowered to obtain modified polyester resin A;

[0041] (3) 531 g of deionized water was heated to 70-80° C., and the modified polyester resin A was added while being stirred to dissolve, thereby obtaining a zero-VOC aqueous modified polyester dispersion.

[0042] Example 4

[0043] The aqueous modified polyester dispersion was prepared by the following steps:

[0044] (1) 6.5 g of a polyether monoamine with a molecular weight of 1000, 45.7 g of a polyether monoamine with a molecular weight of 3000 and 3.2 g of dimethylolbutyric acid are subjected to reflux reaction at 175-185° C., and after the reaction stops producing water, the reflux solvent is removed by vacuum, and then 21.8 g of epoxy resin E20 is added, and the reaction is continued at 120-130° C. until the active hydrogen reacts completely, thereby obtaining a monoepoxy hydrophilic polymer B;

[0045] (2) 30 g of adipic acid, 80 g of 1,4-cyclohexanedicarboxylic acid, 56.4 g of 2-butyl-2-ethyl-1,3-propanediol, 41.6 g of 3-methyl-1,5-pentanediol and 0.3 g of hypophosphorous acid are heated to 150° C. under nitrogen protection, 0.6 g of dibutyltin dilaurate is added, the temperature is continued to rise to 210-220° C., and the mixture is reacted until the acid value reaches 4-7 mgKOH / , the temperature is lowered to 150-160° C., 3.3 g of tetrahydrophthalic anhydride is added, the mixture is reacted for 1 h, polymer B and 0.3 g of tetrabutylammonium bromide are added for end-capping reaction, the mixture is reacted at 145-155° C. until the acid value no longer decreases, and the temperature is lowered to obtain modified polyester resin A;

[0046] (3) 439 g of deionized water was heated to 70-80° C., and the modified polyester resin A was added while being stirred to dissolve, thereby obtaining a zero-VOC aqueous modified polyester dispersion.

[0047] Comparative Example 1

[0048] A water-based modified polyester dispersion was prepared by a process similar to that of Example 1, except that 58.4 g of a polyether monoamine with a molecular weight of 1000, 8.7 g of dimethylolbutyric acid, and 58.4 g of epoxy resin E20 were used in step (1); and 529 g of deionized water was used in step (3).

[0049] Comparative Example 2

[0050] The aqueous modified polyester dispersion was prepared by a process similar to that of Example 2, except that 130.7 g of a polyether monoamine with a molecular weight of 2000, 8.8 g of dimethylol propionic acid, and 29.7 g of epoxy resin E44 were used in step (1); and 587.6 g of deionized water was used in step (3).

[0051] Comparative Example 3

[0052] The aqueous modified polyester dispersion was prepared by a process similar to that of Example 2, except that 73.6 g of 2-butyl-2-ethyl-1,3-propanediol, 54.3 g of 3-methyl-1,5-pentanediol, and 11.7 g of maleic anhydride were used in step (2); and 741.1 g of deionized water was used in step (3).

[0053] The basic indexes of the aqueous modified polyester dispersions obtained in Examples 1-4 and Comparative Examples 1-3 were tested, and the results are shown in Table 1 below:

[0054] Table 1 Test results of basic indicators of water-based modified polyester dispersion

[0055]

[0056]

[0057] The detection method for storage stability at 50°C is as follows: the dispersion is placed in a 500 ml container and covered tightly, stored in a constant temperature oven at 50°C, and then cooled at room temperature for 3 hours to observe whether the dispersion is stratified and coarse particles are produced. If no stratification or coarse particles are produced, it is considered to be storage stable.

[0058] Furthermore, the obtained water-based modified polyester dispersion is added to the coating to measure the performance of the paint film. The measuring method is as follows:

[0059] (1) 50 parts by weight of aqueous modified polyester dispersion, 9 parts by weight of amino resin (303), 0.2 parts by weight of wetting agent Tego-41000, 0.2 parts by weight of defoaming agent, 0.3 parts by weight of anti-flash rust agent, 0.3 parts by weight of adhesion promoter, 0.2 parts by weight of acid catalyst, 30 parts by weight of resin-free white water slurry and 10 parts by weight of deionized water were uniformly stirred to obtain a coating;

[0060] (2) The prepared coating was applied to a degreased aluminum substrate using a scraper, and baked at 235° C. for 100-120 seconds. The coating film performance was tested according to the test method in HG / T3830-2022. The test results are shown in Table 2 below:

[0061] Table 2 Paint film performance test results

[0062]

[0063]

[0064] It can be seen that the paint film performance of Examples 1-4 is better than that of Comparative Examples 2 and 3.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An aqueous modified polyester dispersion, characterized in that: The method comprises the following raw material components: polyether monoamine, epoxy resin, dimethylol butyric acid and / or dimethylol propionic acid, tetrabutyl ammonium bromide, polyacid, polyol, dibasic acid anhydride and esterification catalyst.

2. The aqueous modified polyester dispersion according to claim 1, characterized in that in, The molar ratio of the hydroxyl groups in the polyol to the carboxyl groups in the polyacid is 1.05-1.25:1, the molar amount of the dibasic acid anhydride is 40-80% of the molar amount of excess alcohol hydroxyl groups, and the molar amount of excess alcohol hydroxyl groups is equal to the molar amount of the hydroxyl groups in the polyol minus the molar amount of the carboxyl groups in the polyacid; and / or, the molar ratio of the polyether monoamine, dimethylolbutyric acid and / or dimethylolpropionic acid, the epoxy resin and the dibasic acid anhydride is 1:1:1:1-1.15; and / or, the mass of the tetrabutylammonium bromide is 0.1-0.5% of the total mass of the raw material components; and / or, the mass of the esterification catalyst is 0.1-0.5% of the total mass of the polyacid and the polyol.

3. The aqueous modified polyester dispersion according to claim 1, characterized in that The invention also comprises an antioxidant, wherein the weight of the antioxidant is 0.1-0.5% of the total weight of the polyacid and the polyol.

4. The aqueous modified polyester dispersion according to claim 3, characterized in that The antioxidant is selected from hypophosphorous acid and / or triphenyl phosphite.

5. The aqueous modified polyester dispersion according to claim 1, characterized in that in, The polyol is selected from one or more of neopentyl glycol, trimethylolpropane, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 2-ethyl-1,3-hexanediol, hexanediol, and 2-butyl-2-ethyl-1,3-propanediol; and / or, the polyacid is selected from one or more of adipic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride; and / or, the esterification catalyst is selected from one or more of dibutyltin oxide, dibutyltin dilaurate, and tetraisopropyl titanate; and / or, the dibasic acid anhydride is selected from one or more of phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride.

6. The aqueous modified polyester dispersion according to claim 1, characterized in that in, The polyether monoamine has an amine value of 0.30-1.08 and / or a molecular weight of 1000-3000; and / or the epoxy resin is a bisphenol A epoxy resin and / or a bisphenol F epoxy resin with an epoxy equivalent of 450-1700.

7. The method for preparing the aqueous modified polyester dispersion according to any one of claims 1 to 6, characterized in that: It includes: (1) reacting the polyether monoamine and the dimethylolbutyric acid and / or dimethylolpropionic acid at 150-200° C. until no water is produced and removing the residual solvent in vacuo, adding the epoxy resin and reacting at 120-130° C. to obtain a monoepoxy hydrophilic polymer; (2) The polyacid and polyol are heated to 145-155° C. under inert atmosphere protection, the esterification catalyst is added, the temperature is raised to 180-220° C. and the reaction is continued until the acid value reaches 2-10 mgKOH / g, the temperature is lowered to 140-160° C. and the dibasic acid anhydride is added, the reaction is continued for 1-1.5 hours, the monoepoxy hydrophilic polymer and tetrabutylammonium bromide are added, the reaction is continued at 140-160° C. until the acid value no longer decreases, and a modified polyester resin is obtained; (3) adding the modified polyester resin into deionized water at 70-90° C. to dissolve the modified polyester resin, thereby obtaining the aqueous modified polyester dispersion.

8. The preparation method according to claim 7, characterized in that: in, Step (2) further comprises heating the antioxidant, the polyacid and the polyol to 145-155° C. under the protection of an inert atmosphere.

9. A zero-volatile water-based coating, comprising the water-based modified polyester dispersion according to any one of claims 1 to 6 or the water-based modified polyester dispersion prepared by the preparation method according to claim 7 or 8.

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