阅读说明：本技术 一种具有高支化度亲水链的环氧乳化剂及其制备方法 (Epoxy emulsifier with high-branching degree hydrophilic chain and preparation method thereof ) 是由 方永勤 蒋盛婕 赵神送 许亮 于 2020-11-06 设计创作，主要内容包括：一种具有高支化度亲水链的环氧乳化剂及其制备方法,原料组成如下：含羟基化合物、二乙醇胺改性环氧树脂、异氰酸酯交联剂和催化剂,其中,含羟基化合物由聚乙二醇、三羟甲基丙烷和2-羟基丙酸组成。在反应器中加入甲苯、二乙醇胺改性环氧树脂、聚乙二醇、催化剂升温至120-150℃回流脱水2小时,之后降温至80-100℃加入异氰酸酯交联剂,反应1小时后加入三羟甲基丙烷和2-羟基丙酸,继续反应3小时后减压蒸馏脱除甲苯。本发明通过构造具有高度支化位阻结构的亲水端,降低了疏水端之间的缔合现象,使乳化剂的疏水端可以更加紧密地吸附于待分散的环氧树脂颗粒表面,从而提高了乳化剂的乳化能力和环氧乳液的离心稳定性和储存稳定性。(An epoxy emulsifier with a highly branched hydrophilic chain and a preparation method thereof, the epoxy emulsifier comprises the following raw materials: the hydroxyl-containing compound comprises a hydroxyl-containing compound, diethanolamine modified epoxy resin, an isocyanate crosslinking agent and a catalyst, wherein the hydroxyl-containing compound consists of polyethylene glycol, trimethylolpropane and 2-hydroxypropionic acid. Adding toluene, diethanol amine modified epoxy resin, polyethylene glycol and a catalyst into a reactor, heating to 120-150 ℃, refluxing and dehydrating for 2 hours, then cooling to 80-100 ℃, adding an isocyanate crosslinking agent, reacting for 1 hour, adding trimethylolpropane and 2-hydroxypropionic acid, continuing to react for 3 hours, and then carrying out reduced pressure distillation to remove toluene. According to the invention, the hydrophilic end with a highly branched steric hindrance structure is constructed, so that the association phenomenon between hydrophobic ends is reduced, and the hydrophobic end of the emulsifier can be more closely adsorbed on the surface of the epoxy resin particles to be dispersed, thereby improving the emulsifying capacity of the emulsifier and the centrifugal stability and storage stability of the epoxy emulsion.)

1. The epoxy emulsifier with a highly branched hydrophilic chain is characterized by comprising the following raw materials in parts by mass: 100 parts of hydroxyl-containing compound, 50-80 parts of diethanolamine modified epoxy resin, 15-30 parts of isocyanate crosslinking agent and 1-5 parts of catalyst, wherein the 100 parts of hydroxyl-containing compound comprises 70-80 parts by mass of polyethylene glycol, 15-20 parts by mass of trimethylolpropane and 5-10 parts by mass of 2-hydroxypropionic acid.

2. The epoxy emulsifier with highly branched hydrophilic chains according to claim 1, wherein the diethanolamine modified epoxy resin is prepared by the following steps: 100 parts by mass of bisphenol A type epoxy resin and 30-50 parts by mass of diethanolamine are reacted at 40 ℃ until the epoxy value of the system is constant, wherein the bisphenol A type epoxy resin is one of E20, E44 and E51.

3. The epoxy emulsifier with a highly branched hydrophilic chain according to claim 1, wherein the polyethylene glycol is one of polyethylene glycol 2000, polyethylene glycol 4000 and polyethylene glycol 8000.

4. The epoxy emulsifier with highly branched hydrophilic chains according to claim 1, wherein the isocyanate crosslinking agent is one of toluene diisocyanate, isophorone diisocyanate and diphenylmethane diisocyanate.

5. The epoxy emulsifier with highly branched hydrophilic chains according to claim 1, wherein the catalyst is one of dibutyltin dilaurate and stannous octoate.

6. The process for preparing an epoxy emulsifier with highly branched hydrophilic chains according to any of claims 1 to 5, wherein the steps are as follows: adding toluene, diethanolamine modified epoxy resin, polyethylene glycol and a catalyst into a reactor with an oil-water separator, heating to 120-150 ℃, refluxing and dehydrating for 2 hours, then cooling to 80-100 ℃, adding an isocyanate cross-linking agent, reacting for 1 hour, adding trimethylolpropane and 2-hydroxypropionic acid, continuing to react for 3 hours, and then carrying out reduced pressure distillation to remove toluene, thereby obtaining the epoxy emulsifier with a high branching degree hydrophilic chain, wherein the mass ratio of the toluene to the diethanolamine modified epoxy resin is 6: 1.

Technical Field

The invention relates to the technical field of epoxy resin emulsifiers, in particular to an epoxy emulsifier with a highly branched hydrophilic chain and a preparation method thereof.

Background

The main preparation method of the aqueous epoxy emulsion is to emulsify the epoxy resin into corresponding aqueous dispersion by means of a special epoxy emulsifier. The technical scheme disclosed at present is that epoxy resin or glycidyl ether with a similar structure is used as a hydrophobic end, PEG or other hydrophilic structures with hydroxyl groups are used as hydrophilic ends to construct a nonionic epoxy emulsifier, and the whole design idea is to solve the emulsification problem of the epoxy resin according to the corresponding relation between the HLB value and the emulsification capacity.

Due to the lack of strongly polar carbonyl and carboxyl groups, only moderately polar epoxy and secondary hydroxyl groups, in the molecular structure of epoxy resins, the hydration layer formed on the surface is unstable. The emulsifying property to the epoxy resin can only be solved by adjusting the HLB value of the emulsifier, and the long-term storage stability of the emulsion can not be ensured. The long term storage stability of epoxy emulsions is further dependent on the ability of the hydrophobic end of the emulsifier to bind to the surface of the epoxy particles. During storage, when the hydrophobic end of the emulsifier is desorbed from the surface of the resin particles, the viscous epoxy resin particles are easy to agglomerate, so that emulsion breaking and sedimentation are caused.

The epoxy resin is used as the hydrophobic end of the nonionic emulsifier, and the hydrophobic end forms a stable micelle structure through the association effect of hydrogen bonds, so that the binding capacity of the resin to be dispersed and the hydrophobic end of the emulsifier is reduced.

Epoxy resin is an important crosslinkable material, and a product obtained by crosslinking and curing the epoxy resin has the advantages of stable chemical property, high bonding strength, strong corrosion resistance and the like, so that the epoxy resin is widely applied to various fields of chemical industry, electronics, anticorrosive coatings and the like. The epoxy resin has a large molecular weight and a too hydrophobic structure, and needs to be diluted by organic solvents such as toluene and the like when in use, thereby causing a serious environmental pollution problem.

There are two main methods for the hydration of epoxy resins: (1) introducing hydrophilic groups such as carboxyl and the like on the surface of the epoxy resin in a grafting modification mode to prepare the water-based epoxy resin with self-emulsifying capacity; (2) an aqueous dispersion is prepared by dispersing an epoxy resin in water with the aid of an emulsifier.

The commonly used epoxy emulsifier generally uses epoxy resin as a hydrophobic end and polyethylene glycol as a hydrophilic end, and the nonionic epoxy special emulsifier is formed by connecting the epoxy resin with the polyethylene glycol. Chinese patent publication No. CN110240711 discloses a water-based epoxy emulsifier and preparation and application thereof, the method takes epoxy resin and monoglycidyl ether as hydrophobic ends, takes polyether amine, phosphoric acid and polyethylene glycol diglycidyl ether as hydrophilic ends, and synthesizes the epoxy emulsifier with phosphate groups by taking the polyethylene glycol diglycidyl ether as a connecting structure.

Chinese patent publication No. CN 110054960A discloses a preparation method of an aqueous epoxy resin aqueous dispersion, wherein an epoxy emulsifier is formed by ring-opening polycondensation of hydrophilic polyether polyol and epoxy resin under the catalysis of lewis acid. The emulsifier prepared by the method needs to further react with raw materials such as amide intermediate, aromatic polyol, propylene glycol methyl ether and the like to obtain the water-based epoxy emulsion.

Chinese patent publication No. CN 109868654A discloses an aqueous epoxy sizing agent and a preparation method thereof, wherein the hyperbranched emulsifier is synthesized by reacting polyethylene glycol, a polyfunctional modifier, an epoxy compound and a catalyst, wherein the polyfunctional modifier is a polyhydroxycarboxylic acid such as dimethylolpropionic acid, trihydroxybenzoic acid, itaconic acid, maleic acid and citric acid; the epoxy compound is a hydrophobic structure with epoxy groups, such as trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, pentaerythritol glycidyl ether, epoxy resin and the like; the catalyst is peroxide or Lewis acid-base which can promote the ring opening of epoxy functional group, such as ammonium persulfate, potassium persulfate, tetrabutylammonium bromide, triphenyl phosphonium bromide, boron trifluoride ether and the like. The hydrophobic end of the emulsifier prepared by the method is glycidyl ether with a polyepoxy group, the hydrophilicity of the emulsifier after condensation with polybasic acid and polyethylene glycol is too strong, the binding capacity of the hydrophobic end and epoxy resin is poor, and dispersing aids such as auxiliary emulsifier and hydroxyethyl cellulose are needed in the emulsifying process.

Chinese patent publication No. CN 104479136A discloses a nonionic epoxy emulsifier and a preparation method thereof, bisphenol A type epoxy resin and diglycidyl ether are used as hydrophobic ends, amino-terminated polyethylene glycol is simultaneously used as a hydrophilic end and a connecting structure, and the hydrophilic end and the hydrophobic end are connected together in an amino ring-opening mode. Compared with the traditional epoxy-polyethylene glycol structure, the emulsifier prepared by the method only changes the connection mode of the hydrophilic end and the hydrophobic end, and fails to further improve the emulsifying capacity.

Chinese patent publication No. CN 104389176A discloses an emulsion type carbon fiber sizing agent containing graphene oxide, wherein the preparation method of the epoxy emulsifier is to connect the hydrophilic and hydrophobic ends under the action of diisocyanate by using epoxy resin as the hydrophobic end and using polyethylene glycol and alkylphenol ethoxylate as the hydrophilic end. The emulsifier prepared by the method is of a linear structure, and is easy to separate from the surface of the resin due to the association of the hydrophilic end and the hydrophobic end and exists in an independent micelle structure in a water phase.

Chinese patent publication No. CN 107189084A discloses an aqueous epoxy emulsion prepared from an emulsifier containing isocyanate diepoxy functional groups, which is synthesized from epoxy resin, 2, 4-toluene diisocyanate and polyethylene glycol monomethyl ether. The emulsifier prepared by the method has a short hydrophilic chain segment and is difficult to provide a stable hydration protective layer for epoxy particles.

Because the molecular structure of the epoxy resin lacks strong polar carbonyl and carboxyl, and is only medium polar epoxy group and secondary hydroxyl, a hydration layer formed on the surface is unstable, and when the hydrophobic end of the emulsifier is desorbed from the surface of the resin particles, the viscous resin particles are easy to agglomerate, so that emulsion breaking and sedimentation are caused. On the other hand, the epoxy resin is taken as the hydrophobic end of the nonionic emulsifier, and the epoxy resin is easy to form a stable micelle structure through a hydrogen bond association effect, so that the binding capacity of the resin to be dispersed and the hydrophobic end of the emulsifier is reduced.

Disclosure of Invention

The technical problem to be solved is as follows: aiming at the technical problems, the invention provides an epoxy emulsifier with a highly branched hydrophilic chain and a preparation method thereof, and the hydrophilic group with a branched spatial structure is introduced to weaken the binding capacity of a hydrophobic end in an emulsifier micelle, so that the emulsifier can be more uniformly distributed in a water phase, and a long-term and effective hydrophilic protective layer is provided for an epoxy emulsion.

The technical scheme is as follows: an epoxy emulsifier with a highly branched hydrophilic chain comprises the following raw materials in parts by mass: 100 parts of hydroxyl-containing compound, 50-80 parts of diethanolamine modified epoxy resin, 15-30 parts of isocyanate crosslinking agent and 1-5 parts of catalyst, wherein the 100 parts of hydroxyl-containing compound comprises 70-80 parts by mass of polyethylene glycol, 15-20 parts by mass of trimethylolpropane and 5-10 parts by mass of 2-hydroxypropionic acid.

Preferably, the preparation method of the diethanolamine modified epoxy resin comprises the following steps: 100 parts by mass of bisphenol A type epoxy resin and 30-50 parts by mass of diethanolamine are reacted at 40 ℃ until the epoxy value of the system is constant, wherein the bisphenol A type epoxy resin is one of E20, E44 and E51.

Preferably, the polyethylene glycol is one of polyethylene glycol 2000, polyethylene glycol 4000 and polyethylene glycol 8000.

Preferably, the isocyanate crosslinking agent is one of toluene diisocyanate, isophorone diisocyanate and diphenylmethane diisocyanate.

Preferably, the catalyst is one of dibutyltin dilaurate and stannous octoate.

The preparation method of the epoxy emulsifier with the highly branched hydrophilic chain comprises the following steps: adding toluene, diethanolamine modified epoxy resin, polyethylene glycol and a catalyst into a reactor with an oil-water separator, heating to 120-150 ℃, refluxing and dehydrating for 2 hours, then cooling to 80-100 ℃, adding an isocyanate cross-linking agent, reacting for 1 hour, adding trimethylolpropane and 2-hydroxypropionic acid, continuing to react for 3 hours, and then carrying out reduced pressure distillation to remove toluene, thereby obtaining the epoxy emulsifier with a high branching degree hydrophilic chain, wherein the mass ratio of the toluene to the diethanolamine modified epoxy resin is 6: 1.

has the advantages that: (1) according to the invention, the hydrophobic end epoxy resin is modified by diethanolamine, and the ring opening effect of the diethanolamine and epoxy is utilized to change the terminal position from an epoxy group to a primary hydroxyl group with higher reaction activity, so that the reaction activity of the hydrophobic end and an isocyanate group is improved, and the distribution uniformity of the hydrophilic-hydrophobic end in connection is improved.

(2) According to the invention, trimethylolpropane, polyethylene glycol, 2-hydroxypropionic acid and diethanol amine are adopted to jointly construct a highly branched hydrophilic structure under the action of isocyanate, and the modified hydrophobic end is connected with the polyethylene glycol, the trimethylolpropane and the 2-hydroxypropionic acid to form the emulsifier with the branched hydrophilic structure under the catalysis of tin salt by utilizing the reaction characteristic of NCO and-OH, so that the binding capacity of the hydrophobic end in a micelle structure can be reduced, the emulsifier can be more uniformly distributed in a water phase, and the emulsifying capacity and the stability of the emulsion are improved.

(3) The epoxy emulsifier prepared by the invention can improve the storage stability of the emulsion, can avoid the emulsifier phase separation phenomenon in the film-forming drying process, and is beneficial to approaching and fusing resin particles. The glossiness (60 ℃) of the waterborne epoxy emulsion prepared by the invention can be improved to 85% from 60% of a commercial product after the waterborne epoxy emulsion is cured into a film.

Drawings

FIG. 1 is a schematic structural diagram of an epoxy emulsifier having a branched hydrophilic structure prepared in example 1;

FIG. 2 shows the preparation of epoxy emulsifier with branched hydrophilic structure from example 1¹H NMR spectrum;

FIG. 3 is a graph showing the particle size distribution of the emulsion prepared in example 1.

Detailed Description

The invention is further described below with reference to the accompanying drawings and specific embodiments. The epoxy resins E20, E44, E51 used in the examples and comparative examples were purchased from Nantong star plastics, Inc.; polyethylene glycol 2000, 4000, 8000 were purchased from okay Limited Liaog Yang; toluene, diethanolamine, trimethylolpropane and 2-hydroxypropionic acid are all commercially available analytical reagents.

Example 1

(1) Adding 100g E44 bisphenol A epoxy resin and 30 g of diethanolamine into a reactor, heating to 40 ℃ and reacting until the epoxy value of the system is constant to obtain diethanolamine modified E44 epoxy resin;

(2) adding 300g of toluene, 50g of diethanolamine modified E44 epoxy resin, 70g of polyethylene glycol 2000 and 1g of dibutyltin dilaurate into a reactor with an oil-water separator, heating to 120-150 ℃, refluxing and dehydrating for 2 hours, then cooling to 80-100 ℃, adding 15g of toluene diisocyanate, reacting for 1 hour, adding 20g of trimethylolpropane and 10 g of 2-hydroxypropionic acid, continuing to react for 3 hours, and then carrying out reduced pressure distillation to remove toluene, thus obtaining the epoxy emulsifier with a highly branched hydrophilic chain.

Structural schematic diagram of epoxy emulsifier with branched hydrophilic structure prepared in this example referring to fig. 1, of epoxy emulsifier with branched hydrophilic structure¹The H NMR spectrum is shown in FIG. 2, and the particle size distribution of the prepared emulsion is shown in FIG. 3. As can be seen from FIG. 2, the signal peaks at chemical shifts 1.2-1.7 are the saturated alkane C-H signals in bisphenol A epoxy resin; the signal peak with the chemical shift of 2.6-2.8 is the saturated C-H signal of the polyoxyethylene ether; the signal peaks of chemical shift 3.8-4.2 are O-H signals of hydroxyl and carboxyl and N-H signals in imide structure; the signal peak of chemical shift 6.5-7.5 is the benzene ring C-H signal in the epoxy resin structure. From FIG. 3, it can be seen that the emulsion prepared by the present invention has a smaller particle size and a narrower distribution width.

Comparative example 1

Adding 300g of toluene, 50g E44 epoxy resin, 70g of polyethylene glycol 2000 and 1g of dibutyltin dilaurate into a reactor with an oil-water separator, heating to 120-150 ℃, refluxing and dehydrating for 2 hours, then cooling to 80-100 ℃, adding 15g of toluene diisocyanate, reacting for 3 hours, and then distilling under reduced pressure to remove toluene, thereby obtaining the unmodified epoxy emulsifier.

Example 2

(1) Adding 100g E20 bisphenol A epoxy resin and 40g of diethanolamine into a reactor, heating to 40 ℃ and reacting until the epoxy value of the system is constant to obtain diethanolamine modified E20 epoxy resin;

(2) adding 300g of toluene, 65g of diethanolamine modified E20 epoxy resin, 75g of polyethylene glycol 8000 and 3g of dibutyltin dilaurate into a reactor with an oil-water separator, heating to 120-150 ℃, refluxing and dehydrating for 2 hours, then cooling to 80-100 ℃, adding 20g of isophorone diisocyanate, reacting for 1 hour, adding 17g of trimethylolpropane and 8 g of 2-hydroxypropionic acid, continuing to react for 3 hours, and then carrying out reduced pressure distillation to remove toluene, thus obtaining the epoxy emulsifier with a highly branched hydrophilic chain.

Example 3

(1) Adding 100g E51 bisphenol A epoxy resin and 50g of diethanolamine into a reactor, heating to 40 ℃ and reacting until the epoxy value of the system is constant to obtain diethanolamine modified E51 epoxy resin;

(2) adding 300g of toluene, 50g of diethanolamine modified E51 epoxy resin, 80g of polyethylene glycol 4000 and 5g of stannous octoate into a reactor with an oil-water separator, heating to 120-phase and 150 ℃, refluxing and dehydrating for 2 hours, then cooling to 80-100 ℃, adding 15g of toluene diisocyanate, reacting for 1 hour, adding 15g of trimethylolpropane and 5g of 2-hydroxypropionic acid, continuing to react for 3 hours, and then carrying out reduced pressure distillation to remove toluene, thus obtaining the epoxy emulsifier with a highly branched hydrophilic chain.

The samples obtained in the above examples and comparative examples were prepared into aqueous epoxy emulsions by the following steps, respectively, for evaluating the properties of the emulsifiers:

in a reactor, 90 g E-44 type epoxy resin and 10 g of the epoxy emulsifier obtained in each example are taken, stirred at 500 r/min and heated to 60 ℃, water is slowly dropped into the reactor to ensure that the solid content of the emulsion reaches 50 percent, and then the water-based epoxy emulsion is obtained after dispersion at 1000 r/min for 30 minutes. The performance of the emulsifier is investigated by emulsion particle size, centrifugal stability and storage stability. The prepared waterborne epoxy emulsion is compounded with the Dow WB8001 curing agent and sprayed on the surface of cold-rolled steel to examine the surface gloss of the coating, and test results are shown in Table 1.

TABLE 1 test results

Item	Particle size/nm	Centrifuge stability/%)	Storage stability of 6 months	Gloss (60 degree/%)
					Example 1	149	0	Not delaminating	85
Comparative example 1	1230	25	Has obvious settlement	53
					Example 2	132	0	Not delaminating	86
Example 3	128	0	Not delaminating	84
					Commercially available epoxy emulsions	262	8	Not delaminating	60

The particle size of the epoxy emulsion was determined using the following method: 1g of epoxy emulsion is diluted to 150 mL by deionized water, 5mL of dispersion is taken, and the particle size of the emulsion is tested by adopting a British Malvern ZEN3600 type nanometer laser particle size and a zeta potential analyzer.

The centrifugal stability of the epoxy emulsion was determined by the following method: 8mL of epoxy emulsion is added into a 15mL centrifuge tube, the mixture is centrifuged at 3000 rpm for 30 minutes, and the volume ratio of supernatant liquid is measured, and the calculation formula is as follows:

U=(A÷8)×100

in the formula: u-volume ratio of supernatant,%;

a-supernatant volume, mL.

The storage stability of the epoxy emulsion was determined by the following method: refer to national standard GB/T6753.3-1986 paint storage stability test method.

In conclusion, it can be seen that: according to the preparation process of the epoxy emulsifier disclosed by the invention, the hydrophilic end with a highly branched steric hindrance structure is constructed, so that the association phenomenon between hydrophobic ends is reduced, and the hydrophobic ends of the emulsifier can be more closely adsorbed on the surfaces of epoxy resin particles to be dispersed, thereby improving the emulsifying capacity of the emulsifier, the centrifugal stability, the storage stability and the film-forming glossiness of the epoxy emulsion.