CN116003720A - A kind of epoxy ester modified aqueous polyurethane emulsion and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of coatings, and in particular relates to an epoxy ester modified water-based polyurethane emulsion and a preparation method thereof. The epoxy ester modified water-based polyurethane emulsion prepared by the present invention uses epoxy ester as a modified material, and epoxy diluent and fatty acid undergo ring-opening esterification to synthesize an epoxy ester intermediate, which is grafted into polyurethane, and undergoes Water-based, to obtain epoxy ester modified water-based polyurethane emulsion, which not only introduces the double building of fatty acid, so that the prepared resin has high reactivity, can be oxidatively cross-linked and cured, and the drying speed is fast, and the epoxy diluent is introduced to improve The anti-corrosion performance of the resin reduces its baking temperature and has the effect of toughening and modifying. The present invention has easy-to-obtain raw materials in the whole preparation process, simple process, environmental protection, and easy industrial promotion and production.

Description

A kind of epoxy ester modified aqueous polyurethane emulsion and preparation method thereof

technical field

The invention belongs to the technical field of coatings, and in particular relates to an epoxy ester modified water-based polyurethane emulsion and a preparation method thereof.

Background technique

Waterborne polyurethane (WPU) uses water as the dispersion medium, is an environmentally friendly green material, has the characteristics of low volatile organic compound content and energy saving, and is widely used in various fields. However, the pure water-based polyurethane emulsion cannot meet the requirements in terms of performance, such as poor mechanical properties of the paint film, poor water resistance, low hardness, etc., so it is necessary to modify the water-based polyurethane. However, at present, various single-modified water-based polyurethane coatings have defects such as water resistance, abrasion resistance, alcohol resistance, adhesion and low hardness in use, and are far from being comparable to solvent-based polyurethane coatings. To obtain water-based polyurethane coatings with better performance, two or more different modification methods can be organically combined, and through complementary advantages, the overall performance of water-based polyurethane coatings (such as water resistance, adhesion, and corrosion resistance) can be improved. sex, etc.). Epoxy diluent has the advantages of high modulus, high strength, good chemical resistance, good thermal stability, etc., and has become an important means to improve the performance of waterborne polyurethane. Epoxy-modified WUP products have been improved in terms of water resistance, solvent resistance, tensile strength, and flexibility, but at the same time have disadvantages such as low hardness and poor weather resistance. At the same time, the fatty acid contains unsaturated double bonds, which can not only participate in the reaction of the prepolymer, but also undergo oxidative crosslinking during curing to form a film, thus improving the water resistance, solvent resistance and mechanical properties of the film. The method of compound modification of water-based polyurethane with epoxy diluent and fatty acid combines the advantages of both, so that the comprehensive performance of water-based polyurethane is optimized.

Contents of the invention

In order to solve the deficiencies of the prior art, the invention provides a preparation method of epoxy ester modified water-based polyurethane emulsion. The epoxy ester modified water-based polyurethane emulsion prepared by the present invention has low VOC content, is safe, non-toxic and environmentally friendly, and has excellent dryness, hardness, adhesion, water resistance and other properties, and can reach or exceed the performance indicators of similar solvent-based coatings .

The technical scheme provided by the present invention is as follows:

A kind of preparation method of epoxy ester modified aqueous polyurethane emulsion, comprises the following steps:

1) Synthesis of epoxy ester modified intermediates.

Put the fatty acid, epoxy diluent, and catalyst into the reaction bottle, heat up the reaction to 120°C, keep warm until the acid value is less than 5mgKOH/g, then cool down and discharge to obtain the epoxy ester modified intermediate.

2) Synthesis of prepolymer

Add epoxy ester intermediates, polyester diols, hydrophilic monomers, and small molecule diols into the reactor and mix evenly, heat up to 100-110°C, vacuum at -0.05-0.07MPa, and dehydrate for 1h; Remove the vacuum, lower the temperature to 65°C, slowly add the diisocyanate into the reactor dropwise, and control the dripping within 1-1.5h; raise the temperature to 80-90°C, and add an appropriate amount of acetone to adjust the viscosity of the system until sampling And measure the NCO content by the di-n-butylamine method, stop the reaction after reaching the theoretical end point, and obtain the polyurethane prepolymer;

3) Neutralization and chain extension

Cool down to 50°C, add neutralizing agent to react for 30-40min; use acetone to adjust to a suitable viscosity, control the temperature at 30-40°C, add deionized ice water and chain extender, and perform chain extension reaction for 30-40min under high-speed stirring ; Heat up to 60-70°C to remove acetone under reduced pressure to obtain a brown transparent or translucent epoxy ester modified water-based polyurethane emulsion.

Among the above technical solutions:

In step 1), epoxy ester is used as the modified material, and an epoxy ester intermediate is synthesized through ring-opening esterification of epoxy diluent and fatty acid, which carries the double building of fatty acid;

In step 2), the epoxy ester intermediate has an alcoholic hydroxyl group, which, together with polyols such as polyester diols and small molecule diols, first reacts with polyisocyanate to generate a polyurethane prepolymer with a relatively low molecular weight;

In step 3), the polyurethane prepolymer undergoes chain extension, and the epoxy ester modifies the aqueous polyurethane emulsion, thereby introducing double building of fatty acid.

In the above technical scheme, the fatty acid described in the synthetic part of the epoxy ester modified intermediate is selected from one or more of linolenic acid, soybean oil acid, dehydrated ricinoleic acid, coconut oil acid, and linoleic acid; the epoxy diluent used Selected from ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, butanediol diglycidyl ether, new One or more of pentanediol diglycidyl ether, 1,2 cyclohexanediol diglycidyl ether or hexanediol diglycidyl ether. ; The catalyst used is a quaternary ammonium salt; wherein, the molar ratio of the fatty acid to the epoxy diluent is 2: (0.96-1); the catalyst accounts for 0.8-1.1% of the total system weight.

In the above technical solution, the raw materials used in the synthesis part of the prepolymer are calculated in parts by weight of the polyurethane prepolymer: 5-20% of epoxy ester intermediate, 40%-50% of polyester diol, hydrophilic monomer Body 3% ~ 5.5%, small molecule diol 3.5 ~ 4.5%, diisocyanate 30 ~ 40%.

In the above technical scheme, the polyester diol used in the synthesis part of the prepolymer includes one or more of polycarbonate diol and polycaprolactone diol, with a molecular weight of 500-2000; The alcohol is one of ethylene glycol, propylene glycol butanediol, hexanediol, and 1,4-cyclohexanedimethanol; the hydrophilic monomer used is dimethylol propionic acid, dimethylol butyric acid A kind of; the diisocyanate used is any one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate or dicyclohexylmethane diisocyanate . A preferred diisocyanate is isophorone diisocyanate.

In the above technical scheme, the neutralizing agent used in the neutralization and emulsification process is triethylamine. The chain extender is ethylenediamine.

The present invention also provides the epoxy ester modified water-based polyurethane emulsion prepared by the above preparation method.

Compared with prior art, the beneficial effect of the present invention is:

The epoxy ester modified water-based polyurethane emulsion prepared by the present invention uses epoxy ester as a modified material, and epoxy diluent and fatty acid undergo ring-opening esterification to synthesize an epoxy ester intermediate, which is grafted into polyurethane, and undergoes Water-based, to obtain epoxy ester modified water-based polyurethane emulsion, which not only introduces the double building of fatty acid, so that the prepared resin has high reactivity, can be oxidatively cross-linked and cured, and the drying speed is fast, and the epoxy diluent is introduced to improve The anti-corrosion performance of the resin reduces its baking temperature and has the effect of toughening and modifying. The present invention has easy-to-obtain raw materials in the whole preparation process, simple process, environmental protection, and easy industrial promotion and production.

Description of drawings

Fig. 1 is the IR spectrogram of the epoxy ester modified aqueous polyurethane emulsion synthesized by the present invention. Among them, 3342cm ^-1 is the stretching vibration absorption peak of NH in the urethane bond; 2931cm ^-1 is the stretching vibration absorption peak of _-CH3 ; 1727cm ^-1 is the stretching vibration absorption peak of -C=O; 1235cm- 1 and 1033 cm ^-1 are the stretching vibration absorption peaks of Ar-O and RO on the aromatic ether, respectively, indicating that the epoxy ester participates in the polyurethane reaction.

Detailed ways

The principles and features of the present invention are described below, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

Example 1

1) Synthesis of epoxy ester intermediate:

Weigh 26.67g of ethylene glycol diglycidyl ether epoxy diluent, 55.94g of linolenic acid and 0.830g of tetrabutylammonium iodide into the reactor with stirrer, thermometer and condenser tube, turn on the stirrer, and mix at a low speed After uniformity, increase the speed to 300r/min; raise the temperature to 120°C, keep the temperature for 2 hours, and measure the acid value to be less than 5mgKOH/g, then cool down and discharge to obtain the epoxy ester modified intermediate.

2) Preparation of epoxy ester modified waterborne polyurethane emulsion

Take the above 1.800g of epoxy ester intermediate, 11.85g of polyadipate diol, 1.05g of 1,4-cyclohexanedimethanol and 1.15g of dimethylolpropionic acid into the reactor and mix evenly, and heat up to 105°C , the vacuum degree is -0.05MPa, dehydration for 1h; remove the vacuum, lower the temperature to 65°C, slowly drop 8.9g of isophorone diisocyanate into the reactor, and control it within 1-1.5h; raise the temperature to 90°C , react for 2 hours, during which you can add an appropriate amount of acetone to adjust the viscosity, until the sample is taken and the NCO content measured by the di-n-butylamine method is 3.7%, then the reaction is stopped; the temperature is lowered to 40°C, and 0.86g of triethylamine is added to react for 30 minutes; the viscosity is adjusted with acetone When the solid content of the system is 45%, control the temperature at 35°C, add 47g of deionized ice water and 0.64g of ethylenediamine, and perform the chain extension reaction for about 35min under high-speed stirring; raise the temperature to about 65°C and remove acetone under reduced pressure to obtain a brown color Transparent epoxy ester modified water-based polyurethane emulsion;

Example 2

1) Synthesis of epoxy ester intermediate:

Weigh 32.232.20g1,2-cyclohexanediol diglycidyl ether epoxy diluent, 55.94g soybean oil and 0.935g tetrabutylammonium bromide and add in the reactor with stirrer, thermometer, condenser, open Stirrer, stir at low speed and mix evenly, then increase the speed to 300r/min; raise the temperature to 120°C, keep the temperature for 2 hours, measure the acid value is less than 5mgKOH/g, cool down and discharge, and the epoxy ester modified intermediate is obtained.

2) Preparation of epoxy ester modified waterborne polyurethane emulsion

Take the above-mentioned 2.900g epoxy ester intermediate, 10.00g polycarbonate diol (T5651), 1.03g 1,4-cyclohexanedimethanol and 1.08g dimethylolpropionic acid into the reactor and mix evenly, and heat up to 105 ℃, the vacuum degree is -0.05MPa, dehydration for 1h; remove the vacuum, cool down to 65°C, slowly add 10.75g of dicyclohexylmethane diisocyanate into the reactor dropwise, and control it within 1~1.5h; raise the temperature to 90 ℃, react for 2 hours, during which you can add an appropriate amount of acetone to adjust the viscosity, stop the reaction until the NCO content is 4.15% after sampling and measured by the di-n-butylamine method; cool down to 40 ℃, add 0.81g triethylamine to react for about 35min; use acetone Adjust the viscosity until the solid content of the system is 45%, control the temperature at 35°C, add 47g of deionized ice water and 0.7g of ethylenediamine, and perform the chain extension reaction for about 35min under high-speed stirring conditions; raise the temperature to about 65°C to remove acetone under reduced pressure, A brown transparent epoxy ester modified water-based polyurethane emulsion was obtained.

Example 3

1) Synthesis of epoxy ester intermediate hair:

Weigh 29.50g of 1,6-hexanediol diglycidyl ether (632), 55.94g of oleic acid and 0.900g of tetrabutylammonium bromide into a reactor equipped with a stirrer, a thermometer and a condenser tube, turn on the stirrer, and After stirring and mixing evenly, increase the rotation speed to 300r/min; heat up to 120°C, keep warm for 2 hours, measure the acid value to be less than 5mgKOH/g, cool down and discharge the material, and the epoxy ester modified intermediate is obtained.

2) Preparation of epoxy ester modified waterborne polyurethane emulsion

Take the above-mentioned 2.87g epoxy ester intermediate, 9.94g polyester diol (1136), 1.02g 1,4-cyclohexanedimethanol and 1.07g dimethylolpropionic acid into the reactor and mix evenly, heat up to 105°C , the vacuum degree is -0.05MPa, dehydration for 1h; remove the vacuum, lower the temperature to 65°C, slowly add 6.93g of toluene diisocyanate into the reactor dropwise, control the dripping within 1-1.5h; raise the temperature to 85°C, and react for 2h During this period, an appropriate amount of acetone can be added to adjust the viscosity until the sample is taken and the NCO content measured by the di-n-butylamine method is 4.03%, then the reaction is stopped; the temperature is lowered to 40°C, and 0.81g triethylamine is added to react for about 35min; the viscosity is adjusted to The solid content of the system is 45%, the temperature is controlled at 35°C, 45g of deionized ice water and 0.68g of ethylenediamine are added, and the chain extension reaction is about 35min under high-speed stirring conditions; the temperature is raised to about 65°C to remove acetone under reduced pressure, and a brown transparent Epoxy ester modified waterborne polyurethane emulsion.

Example 4

Take an appropriate amount of the epoxy ester modified water-based polyurethane emulsion prepared in the above-mentioned Examples 1-3 and directly coat it on the polished tinplate, and test the performance of the varnish. The results are shown in Table 1:

Performance example 1 Example 2 Example 3 Exterior brown transparent lotion brown transparent lotion brown transparent lotion contain 35wt% 38wt% 34wt% baking conditions 80℃×30min 80℃×30min 80℃×30min Appearance of paint film smooth smooth smooth Adhesion Level 1 Level 1 Level 1 pencil hardness 1H 2H 2H Impact resistance (50kg/cm) qualified qualified qualified Water resistance (240h) Non-foaming, non-rusting Non-foaming, non-rusting Non-foaming, non-rusting

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (7)

1. a preparation method for epoxy ester modified water-based polyurethane emulsion, is characterized in that, comprises the following steps: 1) Synthesis of epoxy ester intermediate: Put the fatty acid, epoxy diluent, and catalyst into the reaction bottle, raise the temperature to 115-125°C, keep the temperature until the acid value is less than 5mgKOH/g, then cool down and discharge to obtain the epoxy ester intermediate; 2) Synthesis of prepolymer Add epoxy ester intermediates, polyester diols, hydrophilic monomers, and small molecule diols into the reactor and mix evenly, heat up to 100-110°C, vacuum at -0.05-0.07MPa, and dehydrate; remove Vacuum, lower the temperature to 60-70°C, slowly add diisocyanate into the reactor dropwise, and control the dripping within 1-1.5h; raise the temperature to 80-90°C, and add an appropriate amount of acetone to adjust the viscosity of the system until sampling And stop the reaction after the NCO content reaches the theoretical end point by the di-n-butylamine method to obtain the polyurethane prepolymer; 3) Neutralization and chain extension Cool down to 40-50°C, add neutralizing agent to react for 30-40min; adjust to suitable viscosity with acetone, control temperature at 30-40°C, add deionized ice water and chain extender, and perform chain extension reaction under high-speed stirring for 30 minutes -40min; heat up to 60-70°C to remove acetone under reduced pressure to obtain a brown transparent or translucent epoxy ester modified water-based polyurethane emulsion. 2. the preparation method of epoxy ester modified water-based polyurethane emulsion according to claim 1, is characterized in that, in step 1): The fatty acid used in the synthesis of epoxy ester is selected from one or more of linolenic acid, soybean oil acid, dehydrated ricinoleic acid, coconut oil acid or linoleic acid; The epoxy diluent used is selected from any one in glycol diglycidyl ether; The catalyst used is a quaternary ammonium salt; Wherein, the molar ratio of the fatty acid to the epoxy diluent is 2:(0.96-1); the catalyst accounts for 0.8-1.1% of the total system weight in step 1). 3. the preparation method of epoxy ester modified water-based polyurethane emulsion according to claim 2, is characterized in that: used epoxy diluent includes but not limited to ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether ether, triethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,2 cyclohexanediol diglycidyl ether Glyceryl ether or hexanediol diglycidyl ether. 4. the preparation method of epoxy ester modified water-based polyurethane emulsion according to claim 1, is characterized in that, step 2) in, the raw material used of synthetic prepolymer is calculated according to prepolymer weight percent: epoxy ester intermediate 5-20%, polyester diol 40%-50%, hydrophilic monomer 3%-5.5%, small molecule diol 3.5-4.5%, diisocyanate 30-40%. 5. the preparation method of epoxy ester modified water-based polyurethane emulsion according to claim 4, is characterized in that: The polyester diol used to synthesize the prepolymer includes one or more of polycarbonate diol or polycaprolactone diol, with a molecular weight of 500-2000; The small molecular polyol used is one of ethylene glycol, propylene glycol butanediol, hexanediol or 1,4-cyclohexanedimethanol; The hydrophilic monomer used is one of dimethylol propionic acid or dimethylol butyric acid; The diisocyanate used is any one or a mixture of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate or dicyclohexylmethane diisocyanate. 6. the preparation method of epoxy ester modified water-based polyurethane emulsion according to claim 1, is characterized in that, in step 3): The neutralizing agent used is triethylamine; The chain extender used was ethylenediamine. 7. an epoxy ester modified water-based polyurethane emulsion prepared according to any one of claims 1 to 6.

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