阅读说明：本技术 一种水性不饱和聚酯及其制备方法和应用 (Water-based unsaturated polyester and preparation method and application thereof ) 是由 韦星船 何智瀚 于 2021-09-14 设计创作，主要内容包括：本发明公开了一种水性不饱和聚酯及其制备方法和应用,所述水性不饱和聚酯含有源自不饱和二元酸的结构单元一、源自含羟基脂肪二元酸和/或含羟基脂肪三元酸的结构单元二以及源自多元醇的结构单元三。本发明的水性不饱和聚酯具有优异的水稳定性、高附着力与高柔韧性,水性不饱和聚酯的制备工艺简单,不含有机溶剂,绿色环保,可用作于水性环保UV涂料,具有广阔的市场前景。(The invention discloses a waterborne unsaturated polyester, a preparation method and application thereof, wherein the waterborne unsaturated polyester contains a structural unit I derived from unsaturated dibasic acid, a structural unit II derived from hydroxyl-containing fatty dibasic acid and/or hydroxyl-containing fatty tribasic acid and a structural unit III derived from polyalcohol. The water-based unsaturated polyester disclosed by the invention has excellent water stability, high adhesive force and high flexibility, is simple in preparation process, free of organic solvent, green and environment-friendly, can be used as a water-based environment-friendly UV (ultraviolet) coating, and has wide market prospect.)

1. An aqueous unsaturated polyester characterized by: the water-based unsaturated polyester contains a structural unit I derived from unsaturated dibasic acid, a structural unit II derived from hydroxyl-containing fatty dibasic acid and/or hydroxyl-containing fatty tribasic acid and a structural unit III derived from polyalcohol.

2. The aqueous unsaturated polyester according to claim 1, characterized in that: the molar amount of the structural unit II is 10-20%, preferably 15-20% of the total molar amount of the structural unit I and the structural unit II.

3. The aqueous unsaturated polyester according to claim 2, characterized in that: the total molar weight of the first structural unit and the second structural unit is 1-1.2 times, preferably 1.05-1.2 times of that of the third structural unit.

4. The aqueous unsaturated polyester according to any one of claims 1 to 3, wherein: the unsaturated dibasic acid comprises at least one of itaconic acid and itaconic anhydride.

5. The aqueous unsaturated polyester according to claim 4, wherein: the hydroxyl-containing fatty dibasic acid comprises at least one of malic acid and tartaric acid, and the hydroxyl-containing fatty tribasic acid comprises citric acid.

6. The aqueous unsaturated polyester according to claim 5, wherein: the polyol is C_2～6A polyol.

7. The aqueous unsaturated polyester according to claim 6, characterized in that: the polyhydric alcohol comprises at least one of 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, 2, 3-butylene glycol, 1, 2-pentanediol, 1, 5-pentanediol, neopentyl glycol, 1, 2-hexanediol, and 1, 6-hexanediol, and preferably 1, 6-hexanediol.

8. The method for producing the aqueous unsaturated polyester according to any one of claims 1 to 7, wherein: the method comprises the following steps: and (2) carrying out esterification and polycondensation reaction on unsaturated dibasic acid, hydroxyl-containing fatty dibasic acid and/or hydroxyl-containing fatty tribasic acid and polyalcohol in sequence to obtain the water-based unsaturated polyester.

9. The water-based anticorrosive paint is characterized in that: the raw materials for preparing the water-based anticorrosive paint contain the water-based unsaturated polyester disclosed by any one of claims 1-7.

10. Use of the water-based unsaturated polyester according to any one of claims 1 to 7 in surface finishing of leather, glass or wood.

Technical Field

The invention relates to the technical field of high polymer materials, in particular to water-based unsaturated polyester and a preparation method and application thereof.

Background

Organic coatings are an important component of modern chemical engineering. However, almost all conventional coating systems inevitably contain large amounts of organic solvents or other volatiles. In recent years, with the increasing awareness of environmental protection and the stricter environmental regulations, the traditional solvent-based coating is gradually replaced by the environmental-friendly coating. Meanwhile, as petroleum resources are unsustainable and non-renewable resources, the cost of the high molecular coating in the petroleum resources is increased along with the increasing exhaustion of the petroleum resources, and under the pressure of protecting the environment, reducing the production cost and saving the petroleum resources, the industrial and academic circles are actively exploring the green and sustainable substitutes of petroleum-derived chemicals. The green technologies such as water-based paint technology, renewable materials, UV curing and the like become the first choice and development direction of people because the high-performance paint with high yield, low energy consumption and extremely low VOC emission can be produced.

The UV curing coating has the advantages of high curing speed, energy conservation, environmental protection, wide economic application range and the like, and is widely applied to the fields of printing, packaging, advertising, building materials, electronics and the like. However, the conventional UV curable coating has a high composition viscosity of oligomer, which affects the application of construction, so that an additional small-molecule reactive diluent is required to reduce the viscosity of the system, and the reactive diluent is usually highly irritant and toxic, and cannot be completely cured and migrated in the curing process, which limits the application of the UV curable coating in some fields.

The aqueous UV-curable coating effectively solves the problems of the traditional UV coating by using water as a diluent instead of a reactive diluent. The viscosity of the system is adjusted by controlling the solid content of the coating, and the coating has good construction operability. And the water-based UV coating has low VOC (volatile organic compounds) emission, low toxicity and environmental friendliness, so that the water-based UV coating gradually gets attention of people. However, most of the aqueous UV resins used in the current aqueous UV curable coating are synthesized from petroleum resources, and the preparation of aqueous UV resins using biomass resources is a trend due to the decrease of petroleum resources and environmental problems caused thereby.

The unsaturated polyester has simple preparation process, but has large brittleness and poor toughness. And the unsaturated polyester on the current coating market has poor water solubility, is mainly and intensively applied to the traditional solvent type UV curing coating, and the matched active diluent has certain toxicity, so that the requirements of the safety and the environmental protection of the water-based UV resin are difficult to meet.

Itaconic acid, also known as itaconic acid, is evaluated by the U.S. department of energy as one of the most potential 12 bio-based chemical materials, and the raw material source thereof is wide and regenerated, and now is industrially produced in a biological fermentation manner. Itaconic acid contains two carboxyl groups and unsaturated double bonds, can carry out esterification reaction, addition reaction and polymerization reaction due to the active chemical property, and is an important raw material for preparing various novel high polymer materials. Jingyue Dai et al synthesized various carboxyl-terminated itaconic acid-based waterborne UV resins from itaconic acid and various polyols, and although the coatings exhibited good hardness and adhesion, the prepared products were darker in color and the coatings were brittle. The related technology discloses a preparation method of UV-cured waterborne epoxy itaconic acid resin, which improves the flexibility of a coating and effectively solves the brittleness problem of the coating under the condition of keeping the hardness, but the content of itaconic acid in the resin is lower and only occupies 17-26 percent, the content of biomass is lower, and the main raw material components are still petroleum resources.

In short, most of the unsaturated polyester-based water-based paint products in the existing market are prepared from petroleum resources and cannot meet the requirements of environmental protection, and products synthesized from biomass have the problems of deep color, poor flexibility, low biomass content and the like.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides the water-based unsaturated polyester which is green and environment-friendly, and has high flexibility and high adhesive force.

Meanwhile, the invention also provides a preparation method and application of the water-based unsaturated polyester.

Specifically, the invention adopts the following technical scheme:

the first aspect of the present invention provides an aqueous unsaturated polyester containing a first structural unit derived from an unsaturated dibasic acid, a second structural unit derived from a hydroxyl group-containing fatty dibasic acid and/or a hydroxyl group-containing fatty tribasic acid, and a third structural unit derived from a polyhydric alcohol.

The water-based unsaturated polyester according to the first aspect of the present invention has at least the following advantageous effects:

in the waterborne unsaturated polyester, a structural unit I is derived from unsaturated dibasic acid and can provide unsaturated double bonds for curing, a structural unit II is derived from hydroxyl-containing fatty dibasic acid or hydroxyl-containing fatty tribasic acid, wherein hydroxyl is used as a hydrophilic polar group to improve the water stability of the unsaturated polyester and enable the unsaturated polyester to have good adhesive force, and a flexible chain segment in the hydroxyl-containing fatty dibasic acid and/or the hydroxyl-containing fatty tribasic acid endows the unsaturated polyester with excellent flexibility. Meanwhile, the unsaturated polyester is light yellow, and the problem of dark color of the existing biomass resin is solved.

In some embodiments of the invention, the aqueous unsaturated polyester has a linear backbone structure.

In some embodiments of the present invention, the molar amount of the second structural unit is 10% to 20%, preferably 15% to 20% of the total molar amount of the first structural unit and the second structural unit.

In some embodiments of the present invention, the total molar amount of the first structural unit and the second structural unit is 1 to 1.2 times, preferably 1.05 to 1.2 times of that of the third structural unit.

In some embodiments of the present invention, the starting materials for the preparation of the aqueous unsaturated polyester comprise: unsaturated dibasic acid, hydroxyl-containing fatty dibasic acid or hydroxyl-containing fatty tribasic acid, and polyalcohol. The linear skeleton structure of the water-based unsaturated polyester can be formed after esterification and polycondensation of unsaturated dibasic acid, hydroxyl-containing fatty dibasic acid or hydroxyl-containing fatty tribasic acid and polyalcohol.

In some embodiments of the present invention, the molar amount of the hydroxyl-containing fatty dibasic acid and/or the hydroxyl-containing fatty tribasic acid is 10 to 20%, preferably 15 to 20% of the total molar amount of the unsaturated dibasic acid and the hydroxyl-containing fatty dibasic acid and/or the hydroxyl-containing fatty tribasic acid.

In some embodiments of the present invention, the total molar amount of the unsaturated dibasic acid and the hydroxyl group-containing fatty dibasic acid and/or the hydroxyl group-containing fatty tribasic acid is 1 to 1.2 times, preferably 1.05 to 1.2 times, that of the polyol.

In some embodiments of the invention, the unsaturated dibasic acid comprises at least one of itaconic acid (itaconic acid), itaconic anhydride.

In some embodiments of the invention, the hydroxyl-containing fatty diacid comprises at least one of malic acid, tartaric acid, and the hydroxyl-containing fatty triacid comprises citric acid. Wherein the citric acid is an environment-friendly water-soluble bio-based triacid having 3-COOH and 1-OH groups. The citric acid has low activity of tertiary carboxyl on the structure, does not participate in esterification reaction, acts as a dibasic acid when reacting with polyhydric alcohol, improves the water stability and the adhesive force of unsaturated polyester by taking the tertiary carboxyl and hydroxyl on the citric acid as hydrophilic polar groups, has the function of a flexible chain segment, can improve the flexibility of a coating, and effectively solves the problem of high brittleness of the coating.

In some embodiments of the invention, the polyol is C_2～6A polyol. The carbon chain of the polyhydric alcohol is not suitable to be too long, and the too long carbon chain can influence the crosslinking density of a coating formed after the polyester is cured, so that the performance of the coating is reduced to a certain extent.

In some embodiments of the invention, the polyol comprises at least one of 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 1, 2-pentanediol, 1, 5-pentanediol, neopentyl glycol, 1, 2-hexanediol, 1, 6-hexanediol, preferably 1, 6-hexanediol. The polyhydric alcohol is used for carrying out esterification and polycondensation with unsaturated dibasic acid, hydroxyl-containing fatty dibasic acid and/or hydroxyl-containing fatty tribasic acid, and can also serve as a solvent without adding other organic solvents.

In some embodiments of the present invention, the aqueous unsaturated polyester comprises a first structural unit derived from itaconic acid and/or itaconic anhydride, a second structural unit derived from citric acid, and 1, 6-hexanediol, i.e., the aqueous unsaturated polyester comprises the following preparation raw materials: itaconic acid and/or itaconic anhydride, citric acid, 1, 6-hexanediol.

With this combination of starting materials, the reaction mechanism for itaconic acid, citric acid and 1, 6-hexanediol is as follows:

wherein x, y and z are independently selected from integers of 10-90.

In some embodiments of the present invention, the raw materials for preparing the water-based unsaturated polyester further include at least one of a polymerization inhibitor, an esterification catalyst, and a polycondensation catalyst, preferably a combination of the three.

In some embodiments of the present invention, the polymerization inhibitor comprises at least one of p-diphenol, p-hydroxyanisole, p-tert-butylcatechol, and copper naphthenate, preferably at least one of p-diphenol and p-hydroxyanisole. The dosage of the polymerization inhibitor is 0.3 to 0.7 percent of the total mass of the unsaturated dibasic acid, the hydroxyl-containing fatty dibasic acid and/or the hydroxyl-containing fatty tribasic acid and the polyalcohol.

In some embodiments of the invention, the esterification catalyst comprises at least one of p-toluene sulfonic acid, concentrated sulfuric acid, phosphoric acid, tin oxide. The dosage of the esterification catalyst is 0.3 to 0.7 percent of the total mass of the unsaturated dibasic acid, the hydroxyl-containing fatty dibasic acid and/or the hydroxyl-containing fatty tribasic acid and the polyalcohol.

In some embodiments of the invention, the polycondensation catalyst comprises at least one of dibutyltin dilaurate, antimony ethylene glycol, germanium dioxide, aluminum chloride, tetrabutyl titanate, preferably at least one of dibutyltin dilaurate, tetrabutyl titanate. The dosage of the polycondensation catalyst is 0.3-0.7% of the total mass of the unsaturated dibasic acid, the hydroxyl-containing fatty dibasic acid and/or the hydroxyl-containing fatty tribasic acid and the polyalcohol.

In some embodiments of the present invention, the aqueous unsaturated polyester production feedstock further comprises at least one of a neutralizer, a diluent, an initiator, preferably both.

In some embodiments of the invention, the neutralizing agent comprises at least one of triethylamine, sodium bicarbonate, triethanolamine, ammonia. The dosage of the neutralizer meets the requirement that the neutralization degree of the obtained target product is 80-95%.

In some embodiments of the invention, the initiator comprises a photoinitiator, more specifically at least one of the photoinitiators 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone), 2959 (2-hydroxy-4- (2-hydroxyethoxy) -2-methylpropiophenone), 184 (1-hydroxycyclohexyl phenyl methanone). The dosage of the photoinitiator is 2 to 4 percent of the mass of the water-based unsaturated polyester. By adding the initiator, unsaturated carbon-carbon double bonds in the unsaturated polyester can be crosslinked under certain conditions (such as illumination) and cured to form a film.

In some embodiments of the invention, the diluent is water. The dosage of the diluent is enough to enable the water-based unsaturated polyester to form emulsion with the solid content of 40-60%.

The second aspect of the present invention provides a method for preparing the water-based unsaturated polyester, comprising the steps of: and (2) carrying out esterification and polycondensation reaction on unsaturated dibasic acid, hydroxyl-containing fatty dibasic acid and/or hydroxyl-containing fatty tribasic acid and polyalcohol in sequence to obtain the water-based unsaturated polyester.

More specifically, mixing unsaturated dibasic acid, hydroxyl-containing fatty dibasic acid and/or hydroxyl-containing fatty tribasic acid, polyhydric alcohol, a polymerization inhibitor and an esterification catalyst, and carrying out esterification reaction to obtain a first intermediate product;

mixing the first intermediate product with a polycondensation catalyst, and carrying out a polycondensation reaction to obtain a second intermediate product;

and adjusting the neutralization degree of the second intermediate product to obtain the water-based unsaturated polyester.

In some embodiments of the invention, the step of adjusting the degree of neutralization of the second intermediate product is: adjusting the degree of neutralization of the second intermediate product to 80% -95%.

In some embodiments of the present invention, the step of adjusting the neutralization degree of the second intermediate product further comprises the step of adding a diluent and an initiator for mixing. By adding the initiator, the unsaturated polyester can be cured into a film under certain conditions (such as illumination).

In some embodiments of the invention, the esterification reaction is carried out under a protective atmosphere, for example under a nitrogen, argon atmosphere. The temperature of the esterification reaction is 130-150 ℃, and the reaction is carried out until no water is generated. Preferably, the esterification reaction time is 4-6 h.

In some embodiments of the present invention, the temperature of the polycondensation reaction is 130 to 150 ℃, and the reaction time is 1.5 to 2.5 hours. The polycondensation reaction is carried out under the condition of vacuum pumping, and the pressure is-0.085 to-0.095 MPa.

The third aspect of the invention provides a water-based anticorrosive paint, and the raw materials for preparing the water-based anticorrosive paint contain the water-based unsaturated polyester.

The invention also provides application of the water-based unsaturated polyester in surface finishing of leather, glass or woodware.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention uses simple unsaturated dibasic acid, hydroxyl-containing fatty dibasic acid and/or hydroxyl-containing fatty tribasic acid and polyalcohol as monomers, especially uses renewable resources such as itaconic acid, citric acid, 1, 6-hexanediol and the like to replace the traditional petroleum-based monomers, has low production cost, relieves the consumption pressure of petroleum resources and is beneficial to sustainable development.

(2) According to the invention, the water solubility of unsaturated polyester is improved by adding the flexible chain segment containing hydrophilic groups, the traditional solvent type coating is converted into the water-based coating, the coating is endowed with high adhesion and high flexibility, the obtained product has no obvious change within 2 months, and the water stability is good; the obtained unsaturated polyester is light yellow, overcomes the problem of dark color of the existing biomass resin, and has good comprehensive performance.

(3) The production process adopts a one-pot melting method, only reaction raw materials are required to be added for reaction, other organic solvents are not required to be added, the alcohol raw materials serve as solvents, the synthesis has no VOC emission, the process is green and environment-friendly, and the purification is not required after the preparation, so that the process can be directly used for coating solidification; and the paint can be directly adjusted in viscosity by water without adding an organic solvent for dilution, is simple and rapid, can be used as a water-based environment-friendly UV paint, and has wide market prospect.

Drawings

FIG. 1 is a Fourier transform infrared spectrum of an itaconic acid based aqueous UV unsaturated polyester of examples 1-4;

FIG. 2 is a photograph of an itaconic acid based aqueous UV unsaturated polyester according to examples 1 to 4;

FIG. 3 is a photograph of an itaconic acid based aqueous UV unsaturated polyester according to examples 5 to 7.

Detailed Description

The technical solution of the present invention is further described below with reference to specific examples. The starting materials used in the following examples, unless otherwise specified, are available from conventional commercial sources; the processes used, unless otherwise specified, are conventional in the art.

Example 1

(1) 11.817g of 1, 6-hexanediol, 2.306g of citric acid and 14.051g of itaconic acid are weighed into a 250ml four-neck flask, 0.103g of p-toluenesulfonic acid and 0.141g of p-hydroxyanisole are added, a water separator, a stirrer and a circulating condensing device are connected, the temperature is raised to 140 ℃ under the protection of nitrogen, and the mixture is stirred vigorously for 5 hours to carry out esterification reaction.

(2) After the esterification reaction was completed, 0.141g of dibutyltin dilaurate was weighed into the reactor, and the pressure was reduced to-0.095 MPa and polycondensation was carried out at 140 ℃ for 2 hours.

(3) After the polycondensation reaction is finished, cooling to 50 ℃, adding triethylamine according to the calculated acid value to ensure that the pH value of the target product is 7, adding a proper amount of water to adjust the solid content of the product to 50 percent, and intensively stirring for 1 h. And finally, adding a photoinitiator 1173 for mixing, wherein the mass fraction of the photoinitiator 1173 in the reaction system is 3%, so as to obtain the itaconic acid-based waterborne UV unsaturated polyester.

Example 2

(1) 11.817g of 1, 6-hexanediol, 3.458g of citric acid and 13.270g of itaconic acid are weighed into a 250ml four-neck flask, 0.103g of p-toluenesulfonic acid and 0.143g of p-hydroxyanisole are added, a water separator, a stirrer and a circulating condensing device are connected, the temperature is raised to 140 ℃ under the protection of nitrogen, and the mixture is stirred vigorously for 5 hours to carry out esterification reaction.

(2) After the esterification reaction was completed, 0.143g of dibutyltin dilaurate was weighed into the reactor, and the pressure was reduced to-0.095 MPa and polycondensation was carried out at 140 ℃ for 2 hours.

(3) After the polycondensation reaction is finished, cooling to 50 ℃, adding triethylamine according to the calculated acid value to ensure that the pH value of the target product is 7, adding a proper amount of water to adjust the solid content of the product to 50 percent, and intensively stirring for 1 h. And finally, adding a photoinitiator 1173 for mixing, wherein the mass fraction of the photoinitiator 1173 in the reaction system is 3%, so as to obtain the itaconic acid-based waterborne UV unsaturated polyester.

Example 3

(1) 11.817g of 1, 6-hexanediol, 4.035g of citric acid and 12.880g of itaconic acid are weighed into a 250ml four-neck flask, 0.103g of p-toluenesulfonic acid and 0.144g of p-hydroxyanisole are added, a water separator, a stirrer and a circulating condensing device are connected, the temperature is raised to 140 ℃ under the protection of nitrogen, and the mixture is stirred vigorously for 5 hours to carry out esterification reaction.

(2) After the esterification reaction was completed, 0.144g of dibutyltin dilaurate was weighed into the reactor, and the pressure was reduced to-0.095 MPa and polycondensation was carried out at 140 ℃ for 2 hours.

(3) After the polycondensation reaction is finished, cooling to 50 ℃, adding triethylamine according to the calculated acid value to ensure that the pH value of the target product is 7, adding a proper amount of water to adjust the solid content of the product to 50 percent, and intensively stirring for 1 h. And finally, adding a photoinitiator 1173 for mixing, wherein the mass fraction of the photoinitiator 1173 in the reaction system is 3%, so as to obtain the itaconic acid-based waterborne UV unsaturated polyester.

Example 4

(1) 11.817g of 1, 6-hexanediol, 4.611g of citric acid and 12.490g of itaconic acid are weighed into a 250ml four-neck flask, 0.103g of p-toluenesulfonic acid and 0.145g of p-hydroxyanisole are added, a water separator, a stirrer and a circulating condensing device are connected, the temperature is raised to 140 ℃ under the protection of nitrogen, and the mixture is stirred vigorously for 5 hours to carry out esterification reaction.

(2) After the esterification reaction was completed, 0.145g of dibutyltin dilaurate was weighed into the reactor, and the pressure was reduced to-0.095 MPa and polycondensation was carried out at 140 ℃ for 2 hours.

(3) After the polycondensation reaction is finished, cooling to 50 ℃, adding triethylamine according to the calculated acid value to ensure that the pH value of the target product is 7, adding a proper amount of water to adjust the solid content of the product to 50 percent, and intensively stirring for 1 h. And finally, adding a photoinitiator 1173 for mixing, wherein the mass fraction of the photoinitiator 1173 in the reaction system is 3%, so as to obtain the itaconic acid-based waterborne UV unsaturated polyester.

Example 5

(1) 11.817g of 1, 6-hexanediol, 1.609g of malic acid and 14.051g of itaconic acid are weighed into a 250ml four-neck flask, 0.103g of p-toluenesulfonic acid and 0.137g of p-hydroxyanisole are added, a water separator, a stirrer and a circulating condensing device are connected, the temperature is raised to 140 ℃ under the protection of nitrogen, and the mixture is stirred vigorously for 5 hours to carry out esterification reaction.

(2) After the esterification reaction was completed, 0.137g of dibutyltin dilaurate was weighed into the reactor, and the pressure was reduced to-0.095 MPa and polycondensation was carried out at 140 ℃ for 2 hours.

(3) After the polycondensation reaction is finished, cooling to 50 ℃, adding triethylamine according to the calculated acid value to ensure that the pH value of the target product is 7, adding a proper amount of water to adjust the solid content of the product to 50 percent, and intensively stirring for 1 h. And finally, adding a photoinitiator 1173 for mixing, wherein the mass fraction of the photoinitiator 1173 in the reaction system is 3%, so as to obtain the itaconic acid-based waterborne UV unsaturated polyester.

Example 6

(1) 11.817g of 1, 6-hexanediol, 2.414g of malic acid and 13.270g of itaconic acid are weighed and placed in a 250ml four-neck flask, 0.103g of p-toluenesulfonic acid and 0.138g of p-hydroxyanisole are added, a water separator, a stirrer and a circulating condensing device are connected, the temperature is raised to 140 ℃ under the protection of nitrogen, and the mixture is stirred vigorously for 5 hours to carry out esterification reaction.

(2) After the esterification reaction was completed, 0.138g of dibutyltin dilaurate was weighed into the reactor, and the pressure was reduced to-0.095 MPa and polycondensation was carried out at 140 ℃ for 2 hours.

(3) After the polycondensation reaction is finished, cooling to 50 ℃, adding triethylamine according to the calculated acid value to ensure that the pH value of the target product is 7, adding a proper amount of water to adjust the solid content of the product to 50 percent, and intensively stirring for 1 h. And finally, adding a photoinitiator 1173 for mixing, wherein the mass fraction of the photoinitiator 1173 in the reaction system is 3%, so as to obtain the itaconic acid-based waterborne UV unsaturated polyester.

Example 7

(1) 11.817g of 1, 6-hexanediol, 2.702g of tartaric acid and 13.270g of itaconic acid are weighed into a 250ml four-neck flask, 0.103g of p-toluenesulfonic acid and 0.139g of p-hydroxyanisole are added, a water separator, a stirrer and a circulating condensing device are connected, the temperature is raised to 140 ℃ under the protection of nitrogen, and the mixture is stirred vigorously for 5 hours to carry out esterification reaction.

(2) After the esterification reaction was completed, 0.139g of dibutyltin dilaurate was weighed into the reactor, and the pressure was reduced to-0.095 MPa and polycondensation was carried out at 140 ℃ for 2 hours.

(3) After the polycondensation reaction is finished, cooling to 50 ℃, adding triethylamine according to the calculated acid value to ensure that the pH value of the target product is 7, adding a proper amount of water to adjust the solid content of the product to 50 percent, and intensively stirring for 1 h. And finally, adding a photoinitiator 1173 for mixing, wherein the mass fraction of the photoinitiator 1173 in the reaction system is 3%, so as to obtain the itaconic acid-based waterborne UV unsaturated polyester.

The raw material ratios of examples 1 to 7 are shown in Table 1 below.

TABLE 1 amount of starting materials for itaconic acid based aqueous UV unsaturated polyesters

The itaconic acid based aqueous UV unsaturated polyester prepared in the above example was examined as follows.

(1) Structure of the product

FIG. 1 is a Fourier transform infrared spectrum of itaconic acid based aqueous UV unsaturated polyester of examples 1-4. 3240cm in FIG. 1^-1The broad and large peak is represented as the peak of stretching vibration of-OH in carboxyl group, 2943cm^-1And 2863cm^-1The peak at (A) corresponds to-CH on the polymer chain₂-asymmetric and symmetric stretching vibration of 1731cm^-1The peak corresponds to the stretching vibration of the ester bond C ═ O of the unsaturated polyester, indicating that the esterification reaction between the carboxyl group and the hydroxyl group is successful, most importantly 1637cm^-1And 819cm^-1These two points correspond to the stretching vibration peaks of the carbon-carbon double bond. In summary, the reaction product corresponds to the theoretical molecular structure.

(2) Film forming property

The detection method comprises the following steps: and (3) coating the itaconic acid-based waterborne UV unsaturated polyester on the polished tinplate by using a paint film coater, putting the tinplate into an ultraviolet curing machine for curing to form a film, and further testing the film-forming property of the film. The ultraviolet curing conditions were: the power of the ultraviolet lamp was 1kW, and the distance between the sample and the light source was 20 cm.

The results of measuring the properties of the coating films formed from the itaconic acid based aqueous UV unsaturated polyesters of examples 1 to 7 are shown in tables 2 and 3 below.

Table 2 Performance test results of itaconic acid based aqueous UV unsaturated polyesters of examples 1 to 4

TABLE 3 Performance test results of itaconic acid based waterborne UV unsaturated polyesters of examples 5 to 7

Test results show that by introducing saturated carboxylic acid containing hydroxyl groups such as citric acid, malic acid and tartaric acid into the itaconic acid based aqueous UV unsaturated polyester, the coating is endowed with the characteristics of excellent flexibility, better chemical resistance, high adhesion and the like, and the itaconic acid based aqueous UV unsaturated polyester of each embodiment is light in color, is light yellow transparent emulsion, has no obvious change within 2 months and has good comprehensive performance as shown in figures 2 and 3.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.