阅读说明：本技术 一种烤漆专用水性环氧乳液及其制备方法 (Special water-based epoxy emulsion for baking varnish and preparation method thereof ) 是由 王瑞晓 董双建 蔡颖辉 李玉君 崔国栋 杨云龙 路建 王修慎 于 2020-06-29 设计创作，主要内容包括：本发明属于水性涂料领域,具体涉及一种烤漆专用水性环氧乳液及其制备方法。采用改性的方法制备非离子型乳化剂,进一步制备水性环氧乳液,所得水性环氧乳液具有较高的羟值,可较好的应用于烤漆底漆及面漆(室内应用),粒径在50-500nm之间,具有较好的储存稳定性。打破了常规固体环氧树脂不易水性化的难题,且该方法具有操作简便、环境友好以及可控性高等优点,可应用于水性卷材涂料、防腐涂料等,经济效益明显,应用前景广阔。(The invention belongs to the field of water-based paint, and particularly relates to a special water-based epoxy emulsion for baking paint and a preparation method thereof. The nonionic emulsifier is prepared by a modification method, the water-based epoxy emulsion is further prepared, the obtained water-based epoxy emulsion has a higher hydroxyl value, can be better applied to baking varnish priming paint and finishing paint (indoor application), has a particle size of 50-500nm, and has better storage stability. The method breaks the problem that the conventional solid epoxy resin is not easy to be subjected to water-based treatment, has the advantages of simplicity and convenience in operation, environmental friendliness, high controllability and the like, can be applied to water-based coil coating, anticorrosive coating and the like, and has obvious economic benefits and wide application prospects.)

1. The preparation method of the special waterborne epoxy emulsion for baking paint is characterized by comprising the following steps:

1) preparing a nonionic emulsifier: completely reacting epoxy resin I with a compound A at 50-150 ℃;

2) synthesizing self-emulsifying epoxy resin: adding epoxy resin II and a cosolvent into a reactor, heating to dissolve, controlling the reaction temperature to be 60-120 ℃, adding the nonionic emulsifier prepared in the step 1), dropwise adding secondary amine or alcohol amine with the molar weight equal to that of epoxy groups in reactants, and completely reacting;

3) preparing an emulsion: under the condition of high-speed shearing or dispersion, adding desalted water dropwise into the resin reacted in the step 2) for emulsification;

wherein, the epoxy resin I in the step 1) can be solid epoxy resin or liquid epoxy resin; the compound A is water-based polyether polyol or water-based amine;

in the step 2), the epoxy resin II is solid epoxy resin; the epoxy resin II and the epoxy resin I can be the same or different.

2. The method for preparing the waterborne epoxy emulsion specially used for baking paint according to claim 1, wherein the solid epoxy resin in the step 1) is selected from one or more of E03, E06, E12 and E20; the liquid epoxy resin is one or more of E44, E42 and E51; the epoxy resin II in the step 2) is solid epoxy resin and is selected from one or more of E03, E06, E12 and E20.

3. The preparation method of the special waterborne epoxy emulsion for baking paint as claimed in claim 1, wherein the molar ratio of the epoxy resin I to the compound A is 1-4: 1.

4. The method for preparing the waterborne epoxy emulsion for baking paint as claimed in claim 1, wherein the waterborne polyether polyol in the step 1) is selected from PEG1000, PEG2000 and PEG4000, and the waterborne amine is selected from polyetheramines with an average molecular weight of 800-.

5. The preparation method of the special waterborne epoxy emulsion for baking paint as claimed in claim 1, wherein the amount of the cosolvent used in the step 2) is 0-40 wt% of the epoxy resin II.

6. The preparation method of the special waterborne epoxy emulsion for baking finish according to claim 1, wherein the cosolvent in step 2) is selected from one of ethylene glycol n-butyl ether, ethylene glycol sec-butyl ether, ethylene glycol tert-butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, or a mixture of 2-3 solvents.

7. The method for preparing the special waterborne epoxy emulsion for baking paint as claimed in claim 1, wherein the secondary amine in step 2) is selected from diethylamine, di-N-propylamine, N-methylethylamine; the alcohol amine is selected from ethanolamine, diethanolamine, and N-methylethanolamine.

8. The method for preparing the waterborne epoxy emulsion special for baking paint as claimed in claim 1, wherein the emulsifying temperature in the step 3) is controlled at 10-60 ℃.

9. The preparation method of the special waterborne epoxy emulsion for baking paint as claimed in claim 1, wherein the molar ratio of the epoxy resin I to the compound A in the step 1) is 2-3: 1; the reaction temperature is 80-120 ℃.

10. The method for preparing the waterborne epoxy emulsion special for baking paint as claimed in claim 1, wherein the preferred temperature in step 2) is 110-120 ℃; the emulsification temperature in the step 3) is controlled to be 40-50 ℃.

Technical Field

The invention belongs to the field of water-based paint, and particularly relates to a special water-based epoxy emulsion for baking paint and a preparation method thereof.

Background

Along with the stricter and stricter requirements of the country on environmental protection, the stricter and stricter control on industrial VOC and the criticality of workers on construction environment, the development of the traditional solvent-based coating is limited, and meanwhile, the trend of changing oil into water is also indicated.

The aqueous epoxy emulsion mainly comprises an external emulsifier method and a chemical modification method. The external emulsifier method is a method for realizing the state of O/W in a system by using an external emulsifier, and has two methods, namely a mechanical method and a phase inversion method, and the method is also the earliest preparation method for developing the water-based epoxy emulsion and has the characteristics of simple and convenient process. However, the emulsifier is added externally and has no activity, and remains in the paint film, which affects the performance of the paint film, such as poor solvent resistance, water resistance, mechanical properties and the like.

Another method is chemical modification. In the epoxy emulsion prepared by the method, the emulsifier has epoxy active functional groups and can participate in the reaction, and the performance of the prepared paint film is comparable to that of a solvent type. And the emulsion has good stability, and the particle size can generally reach the nanometer level. The chemical modification method is also the preparation method which is most widely applied at present.

Most of the currently marketed water-based epoxy emulsions are of normal-temperature self-drying type, and the water-based epoxy emulsions applied to baking paint are few in variety because the solid epoxy resin has a large molecular weight and is difficult to emulsify. The invention adopts a chemical modification method to prepare the non-ionic self-emulsifying resin, has the characteristic of easy emulsification, and the obtained water-based epoxy emulsion VOC meets the national standard (<260mg/kg), and the VOC can reach the level of 0VOC in some cases. Has important significance for changing oil into water of the primer in the baking varnish industry.

Disclosure of Invention

The invention discloses a special waterborne epoxy emulsion for baking varnish and a preparation method thereof. The nonionic emulsifier is prepared by a modification method, the water-based epoxy emulsion is further prepared, the obtained water-based epoxy emulsion has a higher hydroxyl value, can be better applied to baking varnish priming paint and finishing paint (indoor application), has a particle size of 50-500nm, and has better storage stability. The method breaks the problem that the conventional solid epoxy resin is not easy to be subjected to water-based treatment, has the advantages of simplicity and convenience in operation, environmental friendliness, high controllability and the like, can be applied to water-based coil coating, anticorrosive coating and the like, and has obvious economic benefits and wide application prospects.

The technical scheme adopted by the invention is as follows:

a preparation method of the special waterborne epoxy emulsion for baking paint comprises the following steps:

1) preparing a nonionic emulsifier: completely reacting epoxy resin I with a compound A at 50-150 ℃; the nonionic emulsifier synthesized by the method can detect and track the reaction degree through infrared spectroscopy, has epoxy and hydroxyl active groups, and can participate in the crosslinking reaction of a paint film;

2) synthesizing self-emulsifying epoxy resin: adding epoxy resin II and a cosolvent into a reactor, heating to dissolve, controlling the reaction temperature to be 60-120 ℃, adding the nonionic emulsifier prepared in the step 1), dropwise adding secondary amine or alcohol amine with the molar weight equal to that of epoxy groups in reactants, and completely reacting; adding secondary amine or alcohol amine dropwise to open the epoxy rings of the epoxy resin and the nonionic emulsifier completely, and increasing the active sites of hydroxyl groups in the resin;

3) preparing an emulsion: under the condition of high-speed shearing or dispersion, adding desalted water into the resin reacted in the step 2) dropwise for emulsification.

Wherein, the epoxy resin I in the step 1) can be solid epoxy resin or liquid epoxy resin; the compound A is water-based polyether polyol or water-based amine;

preferably, the molar ratio of the epoxy resin I to the compound A is 1-4:1, more preferably 2-3: 1;

the solid epoxy resin in the step 1) is selected from one or more of E03, E06, E12, E20 and the like; the liquid epoxy resin is one or more of E44, E42, E51 and the like.

The water-based polyether polyol or the water-based amine in the step 1) is added into the reaction in a dropwise manner so as to avoid cross-linking polymerization, and the reaction temperature is preferably 80-120 ℃.

The water-based polyether polyol in the step 1) is selected from PEG1000, PEG2000 and PEG4000, and the water-based amine is selected from polyether amine with the average molecular weight of 800-2000.

In the step 2), the epoxy resin II is solid epoxy resin and is selected from one or more of E03, E06, E12, E20 and the like; the epoxy resin II and the epoxy resin I can be the same or different.

The dosage of the cosolvent in the step 2) is 0-40 wt% of the epoxy resin II.

The cosolvent in the step 2) is ethylene glycol n-butyl ether, ethylene glycol sec-butyl ether, ethylene glycol tert-butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, etc., one of the solvents or 2-3 mixed solvents is selected, and low-toxicity ethers are preferably selected.

The secondary amine in the step 2) can be diethylamine, di-N-propylamine, N-methylethylamine and the like; the alcohol amine can be ethanolamine, diethanolamine, N-methylethanolamine.

The preferred temperature in step 2) is 110-120 ℃.

In the step 3), the emulsifying temperature is controlled at 10-60 ℃, and preferably 40-50 ℃;

step 3) preparing the aqueous epoxy emulsion by adopting a phase inversion method, and selecting a dispersion machine, a colloid mill and a high-speed shearing emulsifying machine for dispersion; the dispersion speed of the dispersion machine is 500-4000r/min, preferably 800-3000r/min, and more preferably 1000-2500 r/min. In the emulsification method of step 3) provided by the present invention, the dosage of the desalted water can be determined according to the actual situation, and is the prior art in the field, and is not described again.

The cosolvent in the finally prepared water-based epoxy emulsion accounts for 0-20 wt%.

Compared with the prior art, the invention has the following advantages:

(1) the preparation method can prepare the nonionic epoxy emulsion, can also further prepare the cationic epoxy emulsion by neutralizing with organic acid, and has controllable and adjustable preparation process and can be adjusted according to different application requirements.

(2) The preparation method of the invention realizes the preparation of the aqueous emulsion of the high molecular weight solid epoxy resin (such as 604 and 609) and fills the blank in the field.

(3) The preparation process is simple, easy to realize industrialization, and can realize intermittent or semi-continuous production.

Detailed Description

The present invention will be described in further detail with reference to the following examples, but it should not be construed that the scope of the above subject matter is limited to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention. Except as otherwise noted, the following examples were carried out using conventional techniques.