阅读说明：本技术 一种水分散型环氧树脂的制备方法 (Preparation method of water-dispersible epoxy resin ) 是由 李国荣 于 2021-01-14 设计创作，主要内容包括：本发明涉及一种水分散型环氧树脂的制备方法,包括如下步骤：S1.将环氧树脂加入到溶剂中,滴加甲苯二异氰酸酯,得到预聚体；S2.将所述预聚体采用薄膜蒸发器提纯,得到中间产物；S3.向所述中间产物中加入聚乙二醇单甲醚,加热反应后,减压蒸馏,再加入水,得到产物。本发明通过化学改性法,在环氧树脂分子骨架上引入具有材料易得、价廉、亲水性的低分子量聚乙二醇单甲醚,制得具有良好水分散性能、储存稳定、耐水性好的水分散型环氧树脂。(The invention relates to a preparation method of water dispersible epoxy resin, which comprises the following steps: s1, adding epoxy resin into a solvent, and dropwise adding toluene diisocyanate to obtain a prepolymer; s2, purifying the prepolymer by adopting a film evaporator to obtain an intermediate product; and S3, adding polyethylene glycol monomethyl ether into the intermediate product, heating for reaction, performing reduced pressure distillation, and adding water to obtain a product. According to the invention, by a chemical modification method, the low molecular weight polyethylene glycol monomethyl ether with easily available, cheap and hydrophilic materials is introduced to the molecular skeleton of the epoxy resin, so that the water dispersible epoxy resin with good water dispersibility, storage stability and water resistance is prepared.)

1. A preparation method of water dispersible epoxy resin is characterized by comprising the following steps:

s1, adding epoxy resin into a solvent, and dropwise adding the epoxy resin into toluene diisocyanate for reaction to obtain a prepolymer;

s2, purifying the prepolymer by adopting a film evaporator to obtain an intermediate product;

s3, adding polyethylene glycol monomethyl ether into the intermediate product, heating for reaction, removing the solvent, and adding water to obtain a product;

wherein the molar ratio of isocyanate groups in the toluene diisocyanate to hydroxyl groups in the epoxy resin is 6:1-10: 1.

2. The method for preparing a water dispersible epoxy resin according to claim 1, wherein the epoxy resin is an E20 epoxy resin.

3. The method for preparing a water dispersible epoxy resin according to claim 1, wherein the molar ratio of the isocyanate group of the intermediate product to the hydroxyl group of the methoxypolyethylene glycol is 1.05:1 to 1: 1.

4. The method for producing a water-dispersible epoxy resin according to claim 1, wherein the thin film evaporator is a two-stage thin film evaporator.

5. The method for preparing a water dispersible epoxy resin according to claim 1, wherein the solvent is one or more selected from the group consisting of ethyl acetate, butyl acetate, toluene, and xylene.

6. The method for producing an aqueous dispersion epoxy resin according to claim 1, wherein the relative molecular mass of the polyethylene glycol monomethyl ether is less than 600.

7. The method for preparing a water-dispersible epoxy resin as claimed in claim 1, wherein the dropping time in step S1 is 150-180 min.

8. The method for preparing a water dispersible epoxy resin according to claim 1, wherein the reaction temperature of step S1 is 80-90 ℃.

9. The method for preparing a water dispersible epoxy resin according to claim 1, wherein the reaction time of step S1 is 5-7 hours.

10. The method for producing a water dispersible epoxy resin according to claim 1, wherein the reaction of step S3 is performed in an inert gas atmosphere.

Technical Field

The invention belongs to the field of epoxy resin, and particularly relates to a preparation method of water dispersible epoxy resin.

Background

Epoxy resin has excellent comprehensive performance, is a very important class of high polymer materials at present, and is widely applied to the fields of coatings, composite materials, adhesives and the like. However, epoxy resins are insoluble in water and often need to be dissolved in organic solvents such as aromatic hydrocarbons, ketones, or alcohol ethers. The use of the organic solvent is not only high in cost, but also flammable and explosive, so that great potential safety hazards exist, and serious air pollution can be caused due to volatilization of a large amount of organic solvent in the use process. Therefore, the water-based epoxy resin is a very urgent and popular research direction in the field of epoxy resin.

The methods for making epoxy resins into aqueous products can be roughly classified into three categories: direct emulsification, chemical modification and phase inversion. The direct emulsification method is to directly perform forced emulsification on the epoxy resin in water containing an emulsifier by means of a colloid mill, a homogenizer and other equipment to obtain an aqueous epoxy resin emulsion. The method has the advantages of simple process; the defects are that the particle size of latex particles is larger, the latex particles belong to a heterogeneous system with unstable free energy, and the prepared emulsion has poor stability and is easy to coagulate, and the emulsion breaking phenomenon can occur when the emulsion is placed for a long time or centrifuged. CN111040191A discloses a water-based epoxy resin emulsion and a preparation method thereof, wherein 50-55% of epoxy resin by mass ratio is heated and dispersed, 0.5-1.6% of alcohol ether solvent and 5.5-6.5% of composite emulsifier are added, the dispersion is continued, the rotating speed is controlled, the temperature is kept, the temperature is reduced, 38-42% of water is added for phase inversion, and the temperature is kept; and cooling the product, and filtering to obtain the water-based epoxy emulsion. The phase inversion method is characterized in that an emulsifier and epoxy resin are uniformly mixed, water is added into a system under the condition of high shear force, the system is changed from water-in-oil to oil-in-water through phase inversion, and a heterogeneous system with small free energy is formed, so that the system is a stable dilutable system. The preparation of the waterborne epoxy resin emulsion by the phase inversion method needs to add more emulsifier, and has great negative influence on the water resistance of final application.

The chemical modification method is also called self-emulsification method, and some hydrophilic chain segments are introduced to the molecular chain of the epoxy resin through chemical reaction, so that the self-emulsification performance is obtained. The epoxy resin emulsion prepared by the chemical modification method has 3 types of nonionic type, cationic type and anionic type, wherein the domestic research reports of the cationic type are less. The nonionic and anionic epoxy emulsions have simple and reliable preparation processes, and various performances of the prepared emulsions are closer to those of solvent-based epoxy, so that the emulsions become the main research direction in the field of the current water-based epoxy. Depending on the method of introducing the hydrophilic group, the method can be classified into an etherification type, an esterification type and a graft reaction type. The etherification type is mainly characterized in that p-aminobenzoic acid is reacted with epoxy resin, so that carboxyl is introduced into the main chain of the epoxy resin, and the water solubility of the resin is enhanced. The esterification type uses hydroxyl on the main chain of the epoxy resin to react with polybasic acid anhydride, introduces carboxyl on the main chain of the epoxy resin, and obtains the water-based epoxy resin after neutralization by amine. The grafting reaction type is to graft an acrylic monomer onto an epoxy resin main chain through free radical polymerization to obtain the water-based epoxy resin which is not easy to hydrolyze. CN112029070A provides a waterborne epoxy resin, a preparation method thereof and a waterborne epoxy insulating impregnating varnish prepared from the waterborne epoxy resin. The preparation method of the water-based epoxy resin comprises the steps of reacting vegetable oil fatty acid with epoxy resin, and then reacting with a functional hydrophilic monomer to obtain the water-based epoxy resin. CN111499882A provides a preparation method of a nonionic water-based epoxy resin emulsion, which comprises the following steps: firstly, polyethylene glycol monomethyl ether and diisocyanate react, then liquid epoxy resin is added to react to obtain a nonionic active epoxy resin emulsifier, and finally the emulsifier is used for carrying out phase inversion on solid epoxy resin to prepare the water-based epoxy resin emulsion. However, liquid epoxy resins contain only a trace amount of hydroxyl groups, and it is difficult to obtain a sufficient mass fraction of nonionic reactive epoxy resin emulsifier by reacting with polyethylene glycol monomethyl ether-terminated diisocyanate, and thus the effect of final use for phase inversion emulsification of solid epoxy resins is very limited.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a new technical scheme for preparing the water-based epoxy resin. Firstly, epoxy resin with hydroxyl functional groups reacts with much excessive toluene diisocyanate to obtain prepolymer reaction liquid containing excessive toluene diisocyanate monomers. The reason for using toluene diisocyanate is that the reactivity of two isocyanate groups of toluene diisocyanate molecule is different, and the isocyanate group is used in a large excess (relative to the hydroxyl group reacted with the isocyanate group), so that toluene diisocyanate molecule only has active isocyanate group to react with the hydroxyl group of epoxy resin, and the generation of gel and polymer is avoided. Removing excessive free toluene diisocyanate monomer from the obtained prepolymer reaction liquid by using a film evaporator, adding polyethylene glycol monomethyl ether at one time, completely reacting hydroxyl of the polyethylene glycol monomethyl ether with isocyanate groups in the prepolymer, removing an organic solvent by reduced pressure distillation, and adding water under high-speed stirring to form the water-dispersible epoxy resin. Because the polyethylene glycol monomethyl ether is a monohydroxy functional group, the reaction with the isocyanate group in the prepolymer is simple and controllable. Can prepare the water dispersible epoxy resin with good water dispersible performance, storage stability and water resistance.

The invention aims to provide a preparation method of water dispersible epoxy resin, which is realized by the following technical means:

a preparation method of water dispersible epoxy resin comprises the following steps:

s1, adding epoxy resin into a solvent, and dropwise adding the epoxy resin into toluene diisocyanate for reaction to obtain a prepolymer;

s2, purifying the prepolymer by adopting a film evaporator to obtain an intermediate product;

s3, adding polyethylene glycol monomethyl ether into the intermediate product, heating for reaction, removing the solvent, and adding water to obtain a product;

wherein the molar ratio of isocyanate groups in the toluene diisocyanate to hydroxyl groups in the epoxy resin is 6:1-10: 1.

Further, the epoxy resin is E20 epoxy resin.

Further, the molar ratio of the isocyanate group of the intermediate product to the hydroxyl group of the polyethylene glycol monomethyl ether is 1.05:1-1: 1.

Further, the thin film evaporator is a two-stage thin film evaporator.

Further, the solvent is selected from one or more of ethyl acetate, butyl acetate, toluene and xylene.

Further, the relative molecular mass of the polyethylene glycol monomethyl ether is less than 600.

The aim of using polyethylene glycol monomethyl ether with low relative molecular mass is to control the hydrophilicity of the final product not to be too strong, and simultaneously, the final product has higher epoxy group content, thereby being more beneficial to various downstream applications.

Further, the dropping time in step S1 is 150-180 min.

Further, the temperature of the reaction in step S1 is 80-90 ℃.

Further, the reaction time of step S1 is 5-7 h.

Further, the reaction of step S3 is performed in an inert gas atmosphere.

The invention has the beneficial effects that:

according to the invention, by a chemical modification method, the low molecular weight polyethylene glycol monomethyl ether with easily available, cheap and hydrophilic materials is introduced to the molecular skeleton of the epoxy resin, so that the water dispersible epoxy resin with good water dispersibility, storage stability and water resistance is prepared.

Detailed Description

In order to more clearly illustrate the technical solution of the present invention, the following examples are given. The starting materials, reactions and work-up procedures which are given in the examples are, unless otherwise stated, those which are customary on the market and are known to the person skilled in the art.

Example 1

S1, adding 2229.25 kg of toluene diisocyanate and 200 kg of isomeric xylene into a dry reaction kettle, keeping stirring, introducing nitrogen, and heating to 85 ℃; uniformly mixing 1000 kg of E-20 type epoxy resin and 250 kg of ethyl acetate, uniformly dropping the mixture into a reaction kettle at a constant speed to react with toluene diisocyanate, wherein the dropping time is 170min, the reaction time is 6.0h, and the reaction temperature is 85-90 ℃ to obtain a prepolymer;

wherein the molar ratio of isocyanate groups in the toluene diisocyanate to hydroxyl groups in the E-20 type epoxy resin is 8: 1.

s2, removing excessive free toluene diisocyanate monomers from the obtained prepolymer by adopting a two-stage film evaporator until the free toluene diisocyanate in the detected prepolymer reaction liquid is less than 0.5 wt% of the total materials in the reaction system to obtain an intermediate product;

s3, under the protection of nitrogen, adding 1120 kg of polyethylene glycol monomethyl ether (relative molecular mass is less than 600) into the intermediate product at one time, wherein the reaction time is 4h and the reaction temperature is 85-90 ℃. After full reaction, carrying out reduced pressure distillation to remove the organic solvent, and then adding 2300 kg of water under high-speed stirring to form water-dispersible epoxy resin;

wherein, the molar ratio of the isocyanic acid group of the intermediate product to the hydroxyl group of the polyethylene glycol monomethyl ether is 1.04: 1.

example 2

S1, adding 2006.32 kg of toluene diisocyanate and 190 kg of isomeric xylene into a dry reaction kettle, keeping stirring, introducing nitrogen, and heating to 85 ℃; uniformly mixing 800 kg of E-20 type epoxy resin and 200 kg of butyl acetate, and then uniformly dropping the mixture into a reaction kettle to react with toluene diisocyanate at a constant speed, wherein the dropping time is 150min, the reaction time is 6.5h, and the reaction temperature is 85-90 ℃, so as to obtain a prepolymer;

wherein the molar ratio of isocyanate groups in the toluene diisocyanate to hydroxyl groups in the E-20 type epoxy resin is 9: 1.

s2, removing excessive free toluene diisocyanate monomers from the obtained prepolymer by adopting a two-stage film evaporator until the free toluene diisocyanate in the detected prepolymer reaction liquid is less than 0.5 wt% of the total materials in the reaction system to obtain an intermediate product;

s3, adding 896 kilograms of polyethylene glycol monomethyl ether (relative molecular mass is less than 600) into the intermediate product at one time under the protection of nitrogen, wherein the reaction time is 5 hours and the reaction temperature is 85-90 ℃. After full reaction, carrying out reduced pressure distillation to remove the organic solvent, and then adding 2000 kg of water under high-speed stirring to form water-dispersed epoxy resin;

wherein, the molar ratio of the isocyanic acid group of the intermediate product to the hydroxyl group of the polyethylene glycol monomethyl ether is 1.02: 1.

example 3

S1, adding 2507.90 kg of toluene diisocyanate and 250 kg of isomeric xylene into a dry reaction kettle, keeping stirring, introducing nitrogen, and heating to 85 ℃; uniformly mixing 900 kg of E-20 type epoxy resin, 230 kg of isomeric toluene and 230 kg of butyl acetate, uniformly dropping the mixture into a reaction kettle at a constant speed to react with toluene diisocyanate, wherein the dropping time is 180min, the reaction time is 7.0h, and the reaction temperature is 85-90 ℃ to obtain a prepolymer;

wherein the molar ratio of isocyanate groups in the toluene diisocyanate to hydroxyl groups in the E-20 type epoxy resin is 10: 1.

s2, removing excessive free toluene diisocyanate monomer from the obtained prepolymer by adopting a two-stage film evaporator until the free toluene diisocyanate in the detected prepolymer reaction liquid is less than 0.5 wt% of the total amount of the raw materials to obtain an intermediate product;

s3, under the protection of nitrogen, 1008 kilograms of polyethylene glycol monomethyl ether (relative molecular mass is less than 600) is added into the intermediate product at one time, the reaction time is 5 hours, and the reaction temperature is 85-90 ℃. After full reaction, carrying out reduced pressure distillation to remove the organic solvent, and then adding 2050 kg of water while stirring at high speed to form water-dispersible epoxy resin;

wherein, the molar ratio of the isocyanic acid group of the intermediate product to the hydroxyl group of the polyethylene glycol monomethyl ether is 1: 1.

example 4

S1, adding 2013.29 kg of toluene diisocyanate and 200 kg of isomeric xylene into a dry reaction kettle, keeping stirring, introducing nitrogen, and heating to 85 ℃; uniformly mixing 850 kg of E-20 type epoxy resin, 220 kg of isomeric toluene and 220 kg of butyl acetate, uniformly dropping the mixture into a reaction kettle at a constant speed to react with toluene diisocyanate, wherein the dropping time is 180min, the reaction time is 6.5h, and the reaction temperature is 85-90 ℃ to obtain a prepolymer;

wherein the molar ratio of isocyanate groups in the toluene diisocyanate to hydroxyl groups in the E-20 type epoxy resin is 6: 1.

s2, removing excessive free toluene diisocyanate monomers from the obtained prepolymer by adopting a two-stage film evaporator until the free toluene diisocyanate in the detected prepolymer reaction liquid is less than 0.5 wt% of the total materials in the reaction system to obtain an intermediate product;

s3, adding 1360 kg of polyethylene glycol monomethyl ether (relative molecular mass is less than 600) into the intermediate product at one time under the protection of nitrogen, and reacting for 4h at 85-90 ℃. After full reaction, carrying out reduced pressure distillation to remove the organic solvent, and then adding 2500 kilograms of water while stirring at high speed to form water-dispersed epoxy resin;

wherein, the molar ratio of the isocyanic acid group of the intermediate product to the hydroxyl group of the polyethylene glycol monomethyl ether is 1: 1.

comparative example 1

S1, adding 280 kg of toluene diisocyanate and 150 kg of isomeric xylene into a dry reaction kettle, keeping stirring, introducing nitrogen, and heating to 85 ℃; uniformly mixing 500 kg of E-20 type epoxy resin, 100 kg of isomeric xylene and 100 kg of butyl acetate, and then uniformly dripping into a reaction kettle at a constant speed, wherein the dripping time is 170min, the reaction time is 7h, and the reaction temperature is 85-90 ℃ to obtain a prepolymer;

wherein, the molar ratio of the toluene diisocyanate to the hydroxyl in the E-20 type epoxy resin is 2: 1.

s2, removing excessive free toluene diisocyanate monomers from the obtained prepolymer by adopting a two-stage film evaporator until the free toluene diisocyanate in the detected prepolymer reaction liquid is less than 0.5 wt% of the total materials in the reaction system to obtain an intermediate product;

s3, under the protection of nitrogen, adding 800 m of polyethylene glycol monomethyl ether (relative molecular mass is less than 600) into the intermediate product at one time, wherein the reaction time is 5h and the reaction temperature is 85-90 ℃. After the full reaction, the organic solvent is removed by reduced pressure distillation, and then 1450 kg of water is added under high-speed stirring to form the water-dispersed epoxy resin.

Wherein, the molar ratio of the isocyanic acid group of the intermediate product to the hydroxyl group of the polyethylene glycol monomethyl ether is 1: 1.

test example

To examine the properties of the products obtained in examples 1 to 4 and comparative example 1 described above, the following test examples were set.

Wherein the content of the first and second substances,

the water dispersibility and storage stability were tested by: 100g of samples of examples 1 to 4 and comparative example 1 were taken, respectively, and placed in an incubator having a set temperature of 23. + -. 2 ℃ for 6 months, followed by observation thereof and recording of the state of the samples.

The water resistance test method comprises the following steps: the test was carried out with reference to the GB/T22374-2018 standard.

The results obtained are shown in table 1.

TABLE 1 results of performance test of products obtained in examples 1 to 4 and comparative example 1

Therefore, the water dispersible epoxy resin obtained by the technical scheme of the invention has obvious advantages in water dispersibility, storage stability and water resistance compared with the comparative example 1.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.