Oxazoline-containing copolymers, their preparation methods, and their applications as aqueous oxazoline crosslinking agents

Abstract

This invention relates to an oxazoline-containing copolymer, its preparation method, and its application as a waterborne oxazoline crosslinking agent, belonging to the field of waterborne crosslinking agent technology. The oxazoline-containing copolymer of this invention comprises: a) at least one monomer (a) selected from C1-20 alkyl esters and C8-20 vinyl aromatic compounds of (meth)acrylate; b) at least one olefinically unsaturated monomer (b), wherein the olefinically unsaturated monomer (b) contains an oxazoline group; c) at least one olefinically unsaturated monomer (c), wherein the olefinically unsaturated monomer (c) contains a polyether group, and the structure of the olefinically unsaturated monomer (c) is at least one of formula (1). The oxazoline-containing copolymer exhibits excellent water dilution properties and, as a waterborne oxazoline crosslinking agent, can improve the adhesion and hot water resistance of waterborne coatings, inks, and adhesives.

Description

Technical Field

[0001] This invention relates to the field of waterborne crosslinking agent technology, and in particular to copolymers containing oxazoline groups, their preparation methods, and their applications as waterborne oxazoline crosslinking agents. Background Technology

[0002] Waterborne coatings, inks, and adhesives offer significant advantages in environmental performance, drastically reducing volatile organic compound (VOC) emissions and effectively mitigating potential health hazards. However, compared to traditional solvent-based coatings, inks, and adhesives, waterborne systems exhibit marked shortcomings in several key performance aspects, such as adhesion to substrates, abrasion resistance, solvent resistance, and hydrolysis resistance. Waterborne oxazoline crosslinking agents offer an effective solution to these problems. They can undergo crosslinking reactions with carboxyl groups in waterborne resins at high temperatures of 80-120°C, thereby significantly improving the overall performance of the coating. Notably, waterborne oxazoline crosslinking agents possess multiple advantages: they are non-toxic and environmentally friendly, aligning with current green development principles; they also have a long shelf life and can be stored in single-component form, greatly simplifying storage and usage. Given these outstanding advantages, waterborne oxazoline crosslinking agents have become an ideal high-performance waterborne crosslinking agent and have been widely used in related fields.

[0003] Currently, copolymerizing unsaturated monomers containing oxazoline groups with unsaturated monomers containing hydrophilic groups is the main method for preparing waterborne oxazoline-containing polymers. Since oxazoline groups react with carboxyl groups, carboxyl-containing unsaturated monomers are rarely used as hydrophilic monomers for copolymerization. Therefore, introducing suitable non-carboxyl hydrophilic groups is key to preparing waterborne oxazoline-containing polymers. US5300602A and US6548182 disclose methods for synthesizing waterborne oxazoline crosslinking agents, in some embodiments of which are obtained by free radical polymerization of methoxy polyethylene glycol methacrylate, unsaturated monomers containing oxazoline groups, and other (meth)acrylate monomers in an aqueous phase. CN106604943B discloses a method for preparing copolymers containing oxazoline monomers, obtained by free radical polymerization of unsaturated hydrophilic monomers containing sulfonic acid groups (such as sodium 2-acryloylamino-2-propanesulfonate), unsaturated monomers containing oxazoline groups, and other (meth)acrylate monomers in an aqueous phase. However, the above methods all have some drawbacks. For example, the methoxylated polyethylene glycol methacrylate used in US5300602A and US6548182 is relatively expensive, and the excessive amount of unsaturated hydrophilic monomers containing sulfonic acid groups in CN106604943B can lead to a decrease in water resistance, indicating room for improvement in performance. Moreover, methods for introducing hydrophilic groups into waterborne oxazoline-containing polymers are still very rare. Finding new methods to introduce hydrophilic groups is of great significance for the development of high-performance polymers such as waterborne oxazoline crosslinking agents. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to overcome the defects or deficiencies of the prior art and provide a copolymer containing an oxazoline group, a method for preparing the same, and its application as a waterborne oxazoline crosslinking agent. The copolymer containing the oxazoline group, as a waterborne oxazoline crosslinking agent (the active ingredient), is used in waterborne coatings, inks, or adhesive compositions and has excellent water dilution properties, adhesion, and hot water resistance, thereby improving the performance of waterborne coatings, inks, or adhesive compositions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a copolymer containing an oxazoline group, comprising:

[0007] a) at least one monomer selected from C1-20 alkyl esters of (meth)acrylate and C8-20 vinyl aromatic compounds;

[0008] b) at least one olefinic unsaturated monomer (b), said olefinic unsaturated monomer (b) comprising an oxazoline group;

[0009] c) at least one olefinically unsaturated monomer (c), said olefinically unsaturated monomer (c) comprising a polyether group, and said olefinically unsaturated monomer (c) having a structure of at least one of formula (1):

[0010]

[0011] In formula (1), R1 and R2 are each independently hydrogen or methyl; R3 is a hydrocarbon group with 1-8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1-8 carbon atoms; x is 0 or 1; y is 6-68;

[0012] In the oxazoline-containing copolymer, the monomer (a) accounts for 0-40 wt% of the oxazoline-containing copolymer, the olefinic unsaturated monomer (b) accounts for 38-70 wt% of the oxazoline-containing copolymer, and the olefinic unsaturated monomer (c) accounts for 15-50 wt% of the oxazoline-containing copolymer.

[0013] The oxazoline-containing copolymer of the present invention, by introducing an olefinic unsaturated monomer (c) containing a polyether group and having a specific structure of formula (1), enables the oxazoline-containing copolymer to have good water dilution properties and can be used as an effective component of a waterborne oxazoline crosslinking agent in waterborne coatings, inks or adhesive compositions, etc., to improve the adhesion and hot water resistance of waterborne coatings, inks or adhesive compositions, etc.

[0014] In the structure of the olefinic unsaturated monomer (c), i.e., in formula (1), y is limited to 6-68, which is beneficial to ensure the hydrophilicity of the oxazoline-containing copolymer while ensuring the polymerization reactivity of the olefinic unsaturated monomer (c). If the y value is too low, the polymerization of the polyether group is too low, resulting in low hydrophilicity of the oxazoline-containing copolymer, which in turn affects the water dilution of the waterborne oxazoline crosslinking agent. If the y value is too high, the polymerization reactivity of the olefinic unsaturated monomer (c) is too low, and the reaction time for polymerization with other monomers to form the oxazoline-containing copolymer will be longer.

[0015] Through repeated research, the inventors of this invention have discovered that controlling the proportion of the olefinically unsaturated monomer (c) in the oxazoline-containing copolymer to 15-50 wt% is beneficial for ensuring both the hydrophilicity of the oxazoline-containing copolymer and its hot water resistance when used as an effective component of a waterborne oxazoline crosslinking agent in waterborne coatings, inks, or adhesive compositions. If the proportion of the olefinically unsaturated monomer (c) in the oxazoline-containing copolymer is too low, the water dilution of the waterborne oxazoline crosslinking agent will be poor. This may be because the polyether groups contained in the olefinically unsaturated monomer (c) have good hydrophilicity, and a low content will result in insufficient hydrophilicity of the oxazoline-containing copolymer, leading to poor water dilution. Conversely, if the proportion of the olefinically unsaturated monomer (c) in the oxazoline-containing copolymer is too high, the high hydrophilicity of the oxazoline-containing copolymer will also affect the hot water resistance of the prepared coatings, inks, and adhesives.

[0016] Furthermore, by controlling the proportion of the olefinically unsaturated monomer (b) in the oxazoline-containing copolymer to be 38-70 wt%, this invention ensures that the oxazoline-containing copolymer contains a certain amount of oxazoline groups. This facilitates the use of the oxazoline-containing copolymer as an effective component of a water-based oxazoline crosslinking agent in water-based coatings, inks, or adhesive compositions, thus promoting the crosslinking reaction. In the oxazoline-containing copolymer, the monomer (a) accounts for 0-40 wt%, indicating that the monomer (a) can be introduced or not introduced into the oxazoline-containing copolymer, and those skilled in the art can select the appropriate content based on actual needs.

[0017] In a preferred embodiment of the present invention, the monomer (a) is at least one selected from methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, sec-butyl methacrylate, 2-ethylhexyl methacrylate, tridecyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, n-dodecyl methacrylate, benzyl methacrylate, styrene, α-methylstyrene, and vinyltoluene. Preferably, it is at least one selected from methyl methacrylate and ethyl methacrylate.

[0018] As a preferred embodiment of the present invention, the olefinically unsaturated monomer (b) is 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-4,4-dimethyl-2-oxazoline, 2-vinyl-5,5-dimethyl-2-oxazoline, 2-vinyl-4,4,5,5-tetramethyl-2-oxazoline, 2 At least one of isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-4-ethyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-4,4-dimethyl-2-oxazoline, 2-isopropenyl-5,5-dimethyl-2-oxazoline, and 2-isopropenyl-4,4,5,5-tetramethyl-2-oxazoline. Preferably, at least one of 2-isopropyl-2-oxazoline and 2-vinyl-2-oxazoline.

[0019] In a preferred embodiment of the present invention, the olefinically unsaturated monomer (c) is obtained by reacting the carboxyl-containing polyether G with the olefinically unsaturated monomer (b); the structure of the carboxyl-containing polyether G is at least one of formula (2):

[0020]

[0021] In formula (2), R2 is hydrogen or methyl; R3 is a hydrocarbon group with 1 to 8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1 to 8 carbon atoms; x is 0 or 1; y is an integer from 6 to 68.

[0022] The present invention can obtain the olefinic unsaturated monomer (c) by ring-opening reaction of the carboxyl group on the carboxyl-containing polyether G of formula (2) with the oxazoline group of the olefinic unsaturated monomer (b).

[0023] The present invention also provides a method for preparing any of the above-described oxazoline-containing copolymers, comprising the following steps: polymerizing the monomer (a), the olefinically unsaturated monomer (b), and the olefinically unsaturated monomer (c) to obtain the copolymer.

[0024] In this preparation method, the unsaturated double bonds (olefin bonds) of the monomer (a), the olefin unsaturated monomer (b), and the olefin unsaturated monomer (c) are polymerized to obtain the copolymer containing the oxazoline group.

[0025] The present invention also provides another method for preparing the oxazoline-containing copolymer described above, comprising the following steps: reacting the monomer (a), the olefinically unsaturated monomer (b), and the carboxyl-containing polyether G to obtain the copolymer, wherein the olefinically unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether G, and the reaction process involves polymerization of unsaturated double bonds and ring-opening reaction between the carboxyl-containing polyether G and the olefinically unsaturated monomer (b); the structure of the carboxyl-containing polyether G is at least one of formula (2):

[0026]

[0027] In formula (2), R2 is hydrogen or methyl; R3 is a hydrocarbon group with 1 to 8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1 to 8 carbon atoms; x is 0 or 1; y is 6-68.

[0028] In this preparation method, the olefinic unsaturated monomer (c) is indirectly obtained by adding the carboxyl-containing polyether G and a portion of the olefinic unsaturated monomer (b) to undergo a ring-opening reaction. Since the olefinic unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether G, there is still olefinic unsaturated monomer (b) remaining after the carboxyl-containing polyether G has reacted completely. As a result, the oxazoline-containing copolymer obtained is equivalent to the polymerization of the monomer (a), the olefinic unsaturated monomer (b), and the olefinic unsaturated monomer (c).

[0029] This invention also provides the use of any of the above-described oxazoline-containing copolymers in aqueous oxazoline crosslinking agents. Specifically, this invention also provides an aqueous oxazoline crosslinking agent comprising any of the above-described oxazoline-containing copolymers and water, wherein water accounts for 30-90 wt% of the total amount of the oxazoline-containing copolymer and water. By using any of the above-described oxazoline-containing copolymers as the effective component of the aqueous oxazoline crosslinking agent, the aqueous oxazoline crosslinking agent can be applied to water-based coatings, inks, or adhesive compositions, exhibiting excellent water dilution properties, adhesion, and hot water resistance.

[0030] In the aqueous oxazoline crosslinking agent, water accounts for 30-90 wt% of the total amount of the oxazoline-containing copolymer and water. If the water content is too low, the viscosity of the aqueous oxazoline crosslinking agent will be too high. If the water content is too high, the effective component content of the aqueous oxazoline crosslinking agent will be too low, requiring the addition of more aqueous oxazoline crosslinking agent to fully exert its crosslinking effect, which increases the inconvenience of use.

[0031] Furthermore, the aqueous oxazoline crosslinking agent further includes an organic solvent, which accounts for 5-50 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent. The organic solvent may be at least one of alcohols, alcohol ethers, ketones, esters, aromatics, etc., preferably at least one of water-soluble organic solvents such as propylene glycol methyl ether and isopropanol, which will not affect the water dilution property of the aqueous oxazoline crosslinking agent. For environmental protection and low VOC emissions considerations, the organic solvent preferably accounts for 5-35 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0032] The preparation process of the oxazoline-containing copolymer is more advantageous in an aqueous system or a system in which water and organic solvents are mixed. Therefore, while preferably preparing the oxazoline-containing copolymer in an aqueous system or a system in which water and organic solvents are mixed, the present invention can also directly obtain the aqueous oxazoline crosslinking agent of the present invention by adjusting the proportion of water or organic solvent. Specifically:

[0033] The present invention also provides a method for preparing any of the above-mentioned aqueous oxazoline crosslinking agents, comprising the following steps: adding water or water and an organic solvent into a reaction vessel, adding an initiator, heating to 50-90°C, adding (preferably dropwise) a mixture of the monomer (a), the olefinically unsaturated monomer (b), and the olefinically unsaturated monomer (c) into the reaction vessel for reaction, and finally obtaining the aqueous oxazoline crosslinking agent.

[0034] In the reaction process of this preparation method, unsaturated double bonds (olefin bonds) polymerize between monomer (a), olefin unsaturated monomer (b), and olefin unsaturated monomer (c) to obtain the copolymer containing oxazoline groups; in addition, water or water and organic solvent are also contained in the reaction system, so that the final product is the aqueous oxazoline crosslinking agent of the present invention.

[0035] The present invention also provides another method for preparing the aqueous oxazoline crosslinking agent described above, comprising the following steps: adding the carboxyl-containing polyether (G) to a container, adding water or water and an organic solvent, adding an initiator, heating to 50-90°C, adding (preferably dropwise) a mixture of monomer (a) and olefinically unsaturated monomer (b) to a reaction vessel for reaction, wherein the olefinically unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether G, and finally obtaining the aqueous oxazoline crosslinking agent.

[0036] The structure of the carboxyl-containing polyether G is at least one of formula (2):

[0037]

[0038] Wherein, R2 is hydrogen or methyl; R3 is a hydrocarbon group with 1 to 8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1 to 8 carbon atoms; x is 0 or 1; y is an integer from 6 to 68.

[0039] In the reaction process of this preparation method, the monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G simultaneously undergo a ring-opening reaction between the carboxyl-containing polyether G and the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)) and a polymerization reaction of unsaturated double bonds between the monomers. Since the olefinic unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether G, the resulting oxazoline-containing copolymer is equivalent to the copolymer obtained by polymerizing the monomer (a), the olefinic unsaturated monomer (b), and the olefinic unsaturated monomer (c). In addition, the reaction system also contains water or water and an organic solvent, so that the final product is the aqueous oxazoline crosslinking agent of the present invention.

[0040] The present invention also provides the use of any of the above-described aqueous oxazoline crosslinking agents in aqueous coatings, inks, or adhesive compositions. Specifically, the present invention also provides an aqueous coating, ink, or adhesive composition comprising a carboxyl-containing aqueous resin and any of the above-described aqueous oxazoline crosslinking agents.

[0041] As a preferred embodiment of the present invention, the carboxyl-containing waterborne resin may be at least one of carboxyl-containing waterborne acrylic resin, carboxyl-containing waterborne polyurethane resin, carboxyl-containing waterborne polyester resin, etc.

[0042] In a preferred embodiment of the present invention, the aqueous oxazoline crosslinking agent in the waterborne coating, ink, or adhesive composition is 2-10 wt% of the carboxyl-containing aqueous resin. If the proportion of the aqueous oxazoline crosslinking agent in the carboxyl-containing aqueous resin is too high, the cost will increase; if the proportion of the aqueous oxazoline crosslinking agent in the carboxyl-containing aqueous resin is too low, the degree of crosslinking will be insufficient, affecting the water resistance, chemical resistance, and other properties of the waterborne coating, ink, or adhesive composition.

[0043] Furthermore, the water-based coating, ink, or adhesive composition further includes additives, wherein the additives constitute 2-30 wt% of the water-based coating, ink, or adhesive composition. The addition of additives can improve the performance and decorative effect of the water-based coating, ink, or adhesive composition. Preferably, the additives constitute 5-25 wt% of the water-based coating, ink, or adhesive composition.

[0044] As a preferred embodiment, the additives include one or more of defoamers, leveling agents, film-forming aids, or thickeners. The defoamer is present in the water-based coating, ink, or adhesive composition at a proportion of 0.1-1 wt%; the leveling agent is present in the water-based coating, ink, or adhesive composition at a proportion of 0.1-1 wt%; the film-forming aid is present in the water-based coating, ink, or adhesive composition at a proportion of 1-10 wt%; and the thickener is present in the water-based coating, ink, or adhesive composition at a proportion of 0.1-2 wt%. Defoamers eliminate bubbles generated during stirring and reaction; leveling agents act on the interface between liquid and air in water-based coatings, inks, or adhesives to improve the smoothness of the paint film surface and prevent defects such as Bénard vortices; film-forming aids enhance the film-forming properties of water-based coatings, inks, or adhesives and establish an evaporation gradient to improve the surface finish of the coating; thickeners adjust the rheological properties of water-based coatings, inks, or adhesives to improve their anti-sagging and anti-splatter properties.

[0045] As a preferred embodiment, the defoamer is at least one of a polysiloxane defoamer and a mineral oil defoamer; the leveling agent is at least one of a polysiloxane leveling agent and an acrylic leveling agent; the film-forming aid is at least one of ethylene glycol butyl ether, propylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, and dipropylene glycol butyl ether; and the thickener is at least one of a polyurethane thickener, an alkali-swellable acrylic thickener, and bentonite. The above-mentioned defoamer, leveling agent, film-forming aid, and thickener do not represent limitations on the present invention, and those skilled in the art can select other types of defoamers, leveling agents, film-forming aids, and thickeners according to actual needs.

[0046] The present invention also provides a method for preparing any of the above-described water-based coatings, inks or adhesive compositions, comprising the following steps: mixing the components evenly to obtain the water-based coatings, inks or adhesive compositions.

[0047] As an application, the present invention provides an article coated with any of the above-described waterborne coating, ink, or adhesive compositions. The waterborne coating, ink, or adhesive composition, comprising the waterborne oxazoline crosslinking agent, is applied to a substrate surface to form the article.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The oxazoline-containing copolymer described in this invention can be used as an effective component of a water-based oxazoline crosslinking agent in water-based coatings, inks, and adhesive compositions, exhibiting excellent water dilution properties, adhesion, and hot water resistance. Detailed Implementation

[0050] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0051] Example 1

[0052] This embodiment provides an aqueous oxazoline crosslinking agent D1, which is prepared by the following process:

[0053] (1) Preparation of carboxyl-containing polyether G1:

[0054] Nitrogen gas was introduced into the reaction flask, followed by the addition of 187.5 g Clariant M750 (polyethylene glycol monomethyl ether, molecular weight 750), 39.0 g 2,2,6,6-tetramethylpiperidine oxide (TEMPO, Aladdin Chemicals), and 500.0 g dichloromethane. The mixture was heated to reflux, and dry air was introduced. 15.6 g concentrated nitric acid was added over 15 minutes, and the mixture was then heated to reflux for 17 hours. 250.0 g isopropanol was then added, and the mixture was stirred for 1 hour. Volatile components were removed under vacuum to obtain 180.2 g of the product (i.e., carboxyl-containing polyether G1). The acid value was measured to be 72 mg KOH / g, and the calculated carboxyl equivalent was approximately 780.

[0055] Among them, the carboxyl-containing polyether G1 satisfies the general formula (2), and R2 is hydrogen, R3 is methyl, Z is methylene, and the average value of y is... The value is 15.3, and x is 0.

[0056] (2) Preparation of aqueous oxazoline crosslinking agent D1

[0057] Nitrogen gas was passed through the reaction flask, and 25.0 g of carboxyl polyether G1, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and olefinic unsaturated monomer (b) (47.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D1.

[0058] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G1, with a tested acid value of zero, indicating that the carboxyl-containing polyether G1 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G1 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0059] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 43.4 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 28.6 wt% of the oxazoline-containing copolymer.

[0060] The aqueous oxazoline crosslinking agent D1 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids content) of 271. In the aqueous oxazoline crosslinking agent D1 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0061] The aqueous oxazoline crosslinking agent D1 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0062] Example 2

[0063] This embodiment provides an aqueous oxazoline crosslinking agent D2, which is prepared through the following process:

[0064] (1) Preparation of carboxyl-containing polyether G2:

[0065] Nitrogen gas was introduced into the reaction flask, followed by the addition of 43.8 g Clariant M350 (polyethylene glycol monomethyl ether, molecular weight 350), 39.0 g 2,2,6,6-tetramethylpiperidine oxide (TEMPO, Aladdin Chemicals), and 160.0 g dichloromethane. The mixture was heated to reflux, and dry air was introduced. 15.6 g concentrated nitric acid was added over 15 minutes, and the mixture was then heated to reflux for 17 hours. 80.0 g isopropanol was then added, and the mixture was stirred for 1 hour. Volatile components were removed under vacuum to obtain 40.7 g of the product (i.e., carboxyl-containing polyether G2). The acid value was measured to be 148 mg KOH / g, and the calculated carboxyl equivalent was approximately 380.

[0066] Among them, the carboxyl-containing polyether G2 satisfies the general formula (2), and R2 is hydrogen, R3 is methyl, Z is methylene, and the average value of y is... The value is 6.2, and x is 0.

[0067] (2) Preparation of aqueous oxazoline crosslinking agent D2:

[0068] Nitrogen gas was passed through the reaction flask, and 25.0 g of carboxyl polyether G2, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and olefinic unsaturated monomer (b) (47.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D2.

[0069] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G2, with a tested acid value of zero, indicating that the carboxyl-containing polyether G2 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G2 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus obtaining a copolymer containing an oxazoline group.

[0070] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 39.7 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 32.3 wt% of the oxazoline-containing copolymer.

[0071] The aqueous oxazoline crosslinking agent D2 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids content) of 297. In the aqueous oxazoline crosslinking agent D2 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0072] The aqueous oxazoline crosslinking agent D2 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0073] Example 3

[0074] This embodiment provides an aqueous oxazoline crosslinking agent D3, which is prepared through the following process:

[0075] (1) Preparation of carboxyl-containing polyether G3:

[0076] Nitrogen gas was purged into the reaction flask. 375g of Clariant M3000 FL (polyethylene glycol monomethyl ether, molecular weight 3000), 39.0g of 2,2,6,6-tetramethylpiperidine oxide (TEMPO, Aladdin Chemicals), and 160.0g of dichloromethane were added. The mixture was heated to reflux, and dry air was introduced. 15.6g of concentrated nitric acid was added over 15 minutes, and the mixture was then heated to reflux for 17 hours. 80.0g of isopropanol was then added, and the mixture was stirred for 1 hour. Volatile components were removed under vacuum to obtain 356g of the product (i.e., carboxyl-containing polyether G3). The acid value was measured to be 18.5 mg KOH / g, and the calculated carboxyl equivalent was approximately 3030.

[0077] Among them, the carboxyl-containing polyether G3 satisfies the general formula (2), and R2 is hydrogen, R3 is methyl, Z is methylene, and y is the average value. The value is 66.4, and x is 0.

[0078] (2) Preparation of aqueous oxazoline crosslinking agent D3:

[0079] Nitrogen gas was passed through the reaction flask, and 25.0 g of carboxyl polyether G3, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and olefinic unsaturated monomer (b) (47.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D3.

[0080] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G3, with a tested acid value of zero, indicating that the carboxyl-containing polyether G3 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G3 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0081] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 46.1 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 25.9 wt% of the oxazoline-containing copolymer.

[0082] The aqueous oxazoline crosslinking agent D3 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids) of 256. In the aqueous oxazoline crosslinking agent D3 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0083] The aqueous oxazoline crosslinking agent D3 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0084] Example 4

[0085] This embodiment provides an aqueous oxazoline crosslinking agent D4, which is prepared through the following process:

[0086] (1) Preparation of carboxyl-containing polyether G4:

[0087] Nitrogen gas was purged into the reaction flask, and 312.5 g of Clariant B11 / 150 (a copolymer of butyl-terminated ethylene oxide and propylene oxide, molecular weight 2500, ethylene oxide / propylene oxide molar ratio 1:1), 39.0 g of 2,2,6,6-tetramethylpiperidine oxide (TEMPO, Aladdin Chemicals) and 600.0 g of dichloromethane were added. The mixture was heated to reflux, and dry air was purged. 15.6 g of concentrated nitric acid was added over 15 min, and the mixture was then heated to reflux for 17 h. 80.0 g of isopropanol was then added, and the mixture was stirred for 1 h. Volatile components were removed under vacuum to obtain 300.5 g of product (i.e., carboxyl-containing polyether G4). The acid value was tested to be 22.2 mg KOH / g, and the calculated carboxyl equivalent was approximately 2530.

[0088] Among them, the carboxyl-containing polyether G4 satisfies the general formula (2), and R2 is hydrogen and methyl (the molar ratio of hydrogen / methyl is 1:1), R3 is n-butyl, Z is methylene, and the average value of y is... The value is 46.7, and x is 0.

[0089] (2) Preparation of aqueous oxazoline crosslinking agent D4:

[0090] Nitrogen gas was passed through the reaction flask, and 25.0 g of carboxyl polyether G4, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and olefinic unsaturated monomer (b) (47.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D4.

[0091] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G4, with a tested acid value of zero, indicating that the carboxyl-containing polyether G4 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G4 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0092] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 45.9 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 26.1 wt% of the oxazoline-containing copolymer.

[0093] The aqueous oxazoline crosslinking agent D4 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids) of 257. In the aqueous oxazoline crosslinking agent D4 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0094] The aqueous oxazoline crosslinking agent D4 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0095] Example 5

[0096] This embodiment provides an aqueous oxazoline crosslinking agent D5, which is prepared through the following process:

[0097] (1) Preparation of carboxyl-containing polyether G5:

[0098] Nitrogen gas was introduced into the reaction flask, and 750g of Clariant M750 (polyethylene glycol monomethyl ether, molecular weight 750) and 168.2g of methylhexahydrophthalic anhydride were added. The mixture was heated to 120℃ and reacted for 4 hours. Infrared spectroscopy showed that the hydroxyl groups were almost completely converted, and the product (i.e., carboxyl-containing polyether G5) was obtained. The acid value was measured to be 61mgKOH / g, and the carboxyl equivalent was calculated to be approximately 918.

[0099] Among them, the carboxyl-containing polyether G5 satisfies the general formula (2), and R2 is hydrogen, R3 is methyl, and the average value of y is... The value is 15.3, x is 1, and Z is the divalent alicyclic hydrocarbon group with 7 carbon atoms as shown in formula (3):

[0100]

[0101] (2) Preparation of aqueous oxazoline crosslinking agent D5:

[0102] Nitrogen gas was passed through the reaction flask, and 25.0 g of carboxyl polyether G5, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and olefinic unsaturated monomer (b) (47.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D5.

[0103] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G5, with a tested acid value of zero, indicating that the carboxyl-containing polyether G5 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G5 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus obtaining the copolymer containing the oxazoline group.

[0104] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 44.0 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 28.0 wt% of the oxazoline-containing copolymer.

[0105] The aqueous oxazoline crosslinking agent D5 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids) of 268. In the aqueous oxazoline crosslinking agent D5 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0106] The aqueous oxazoline crosslinking agent D5 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0107] Example 6

[0108] This embodiment provides an aqueous oxazoline crosslinking agent D6, which is prepared through the following process:

[0109] (1) Preparation of carboxyl-containing polyether G6:

[0110] Nitrogen gas was passed through the reaction flask, and 750g of Clariant M750 (polyethylene glycol monomethyl ether, molecular weight 750) and 148.1g of phthalic anhydride were added. The mixture was heated to 120℃ and reacted for 4 hours. Infrared spectroscopy showed that the hydroxyl groups were almost completely converted, and the product (i.e., carboxyl-containing polyether G6) was obtained. The acid value was measured to be 62mgKOH / g, and the carboxyl equivalent was calculated to be approximately 898.

[0111] Among them, the carboxyl-containing polyether G6 satisfies the general formula (2), and R2 is hydrogen, R3 is methyl, and the average value of y is... The value is 15.3, x is 1, and Z is the divalent aromatic hydrocarbon group with 6 carbon atoms as shown in equation (4):

[0112]

[0113] (2) Preparation of aqueous oxazoline crosslinking agent D6:

[0114] Nitrogen gas was passed through the reaction flask, and 25.0 g of carboxyl polyether G6, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and olefinic unsaturated monomer (b) (47.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D6.

[0115] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G6, with an acid value of zero, indicating that the carboxyl-containing polyether G6 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G6 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus obtaining the copolymer containing the oxazoline group.

[0116] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 43.9 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 28.1 wt% of the oxazoline-containing copolymer.

[0117] The aqueous oxazoline crosslinking agent D6 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids) of 268. In the aqueous oxazoline crosslinking agent D6 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0118] The aqueous oxazoline crosslinking agent D6 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0119] Example 7

[0120] This embodiment provides an aqueous oxazoline crosslinking agent D7, which is prepared through the following process:

[0121] (1) Preparation of olefinic unsaturated monomers (c1):

[0122] In a reaction flask, an olefinic unsaturated monomer (b) (111.1 g 2-isopropenyl-2-oxazoline), 780.0 g carboxyl-containing polyether G1, and 0.45 g p-methoxyphenol were added. The mixture was heated to 90 °C and reacted for 10 h. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the olefinic unsaturated monomer (c1).

[0123] Among them, the olefinic unsaturated monomer (c1) satisfies the general formula (1), and R1 is methyl, R2 is hydrogen, R3 is methyl, Z is methylene, and y is the average value. The value is 15.3, and x is 0.

[0124] (2) Preparation of aqueous oxazoline crosslinking agent D7:

[0125] Nitrogen gas was passed through the reaction flask, and 79.5 g of water and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate), olefinic unsaturated monomer (b) (43.4 g 2-isopropenyl-2-oxazoline), and 28.6 g olefinic unsaturated monomer (c1) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D7.

[0126] In the reaction process, unsaturated double bonds (olefin bonds) polymerize between monomer (a), olefin unsaturated monomer (b), and olefin unsaturated monomer (c1) to obtain a copolymer containing oxazoline groups.

[0127] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 43.4 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c1) accounts for 28.6 wt% of the oxazoline-containing copolymer.

[0128] The aqueous oxazoline crosslinking agent D7 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids) of 271. In the aqueous oxazoline crosslinking agent D7 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0129] The aqueous oxazoline crosslinking agent D7 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0130] Example 8

[0131] This embodiment provides an aqueous oxazoline crosslinking agent D8, which is prepared through the following process:

[0132] (1) Preparation of olefinic unsaturated monomer (c2):

[0133] In a reaction flask, 97.1 g of 2-vinyl-2-oxazoline, 780.0 g of carboxyl-containing polyether G1, and 0.45 g of p-methoxyphenol were added to an olefinic unsaturated monomer (b). The mixture was heated to 90 °C and reacted for 10 h. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the olefinic unsaturated monomer (c2).

[0134] Among them, the olefinic unsaturated monomer (c2) satisfies the general formula (1), and R1 is hydrogen, R2 is hydrogen, R3 is methyl, Z is methylene, and y is the average value. The value is 15.3, and x is 0.

[0135] (2) Preparation of aqueous oxazoline crosslinking agent D8:

[0136] Nitrogen gas was passed through the reaction flask, 159.0 g of water was added, and the mixture was heated to 80 °C. 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate), olefinic unsaturated monomer (b) (43.4 g 2-vinyl-2-oxazoline), and 28.6 g olefinic unsaturated monomer (c2) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 h. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 h. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D8.

[0137] In the reaction process, unsaturated double bonds (olefin bonds) polymerize between monomer (a), olefin unsaturated monomer (b), and olefin unsaturated monomer (c2) to obtain a copolymer containing oxazoline groups.

[0138] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 43.4 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c2) accounts for 28.6 wt% of the oxazoline-containing copolymer.

[0139] The aqueous oxazoline crosslinking agent D8 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids content) of 237. In the aqueous oxazoline crosslinking agent D8 of this embodiment, water accounts for 61.4 wt% of the total amount of the oxazoline-containing copolymer and water.

[0140] The aqueous oxazoline crosslinking agent D8 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0141] Example 9

[0142] This embodiment provides an aqueous oxazoline crosslinking agent D9, which is prepared through the following process:

[0143] Nitrogen gas was passed through the reaction flask, and 27.0 g of carboxyl polyether G1, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. The olefinic unsaturated monomer (b) (73.0 g of 2-isopropenyl-2-oxazoline) was added dropwise to the reaction vessel at a uniform rate over 2 h. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 h. The acid value was measured to be zero, and the resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D9.

[0144] In this reaction, the olefinic unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether G1, and the acid value is zero, indicating that the carboxyl-containing polyether G1 has completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, both the olefinic unsaturated monomer (b) and the carboxyl-containing polyether G1 undergo ring-opening reactions (forming olefinic unsaturated monomer (c)) and polymerization reactions of unsaturated double bonds (olefin bonds) between the monomers, thus obtaining a copolymer containing oxazoline groups.

[0145] In the oxazoline-containing copolymer, monomer (a) accounts for 0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 69.2 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 30.8 wt% of the oxazoline-containing copolymer.

[0146] The aqueous oxazoline crosslinking agent D9 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids) of 170. In the aqueous oxazoline crosslinking agent D9 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0147] The aqueous oxazoline crosslinking agent D9 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0148] Example 10

[0149] This embodiment provides an aqueous oxazoline crosslinking agent D10, which is prepared through the following process:

[0150] Nitrogen gas was passed through the reaction flask, and 13.5g of carboxyl polyether G1, 79.5g of water, and 79.5g of propylene glycol methyl ether were added. The mixture was heated to 80°C, and 6.0g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (39.3g of methyl methacrylate) and olefinic unsaturated monomer (b) (47.2g of 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80±2°C. After the addition was complete, the mixture was kept at 80±2°C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D10.

[0151] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G1, with a tested acid value of zero, indicating that the carboxyl-containing polyether G1 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G1 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0152] In the oxazoline-containing copolymer, monomer (a) accounts for 39.3 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 45.3 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 15.4 wt% of the oxazoline-containing copolymer.

[0153] The aqueous oxazoline crosslinking agent D10 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids content) of 260. In the aqueous oxazoline crosslinking agent D10 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0154] The aqueous oxazoline crosslinking agent D10 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0155] Example 11

[0156] This embodiment provides an aqueous oxazoline crosslinking agent D11, which is prepared through the following process:

[0157] Nitrogen gas was passed through the reaction flask, and 43.0 g of carboxyl polyether G1, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (9.8 g methyl methacrylate) and olefinic unsaturated monomer (b) (47.2 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent D11.

[0158] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G1, with a tested acid value of zero, indicating that the carboxyl-containing polyether G1 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G1 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0159] In the oxazoline-containing copolymer, monomer (a) accounts for 9.8 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 41.1 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 49.1 wt% of the oxazoline-containing copolymer.

[0160] The aqueous oxazoline crosslinking agent D11 of this embodiment has a solid content of 40% and an oxazoline equivalent (based on solids) of 287. In the aqueous oxazoline crosslinking agent D11 of this embodiment, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0161] The aqueous oxazoline crosslinking agent D11 obtained in this embodiment was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0162] Comparative Example 1

[0163] This comparative example provides an aqueous oxazoline crosslinking agent E1, which is prepared by the following process:

[0164] Nitrogen gas was passed through the reaction flask, and 79.5 g of water and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and unsaturated monomer (b) (72.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 hours. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent E1.

[0165] In the reaction process, unsaturated double bonds are polymerized between monomer (a) and olefinic unsaturated monomer (b) to obtain a copolymer containing oxazoline groups.

[0166] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 72.0 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 0 wt% of the oxazoline-containing copolymer.

[0167] The aqueous oxazoline crosslinking agent E1 of this comparative example has a solid content of 40% and an oxazoline equivalent (based on solids) of 163. In the aqueous oxazoline crosslinking agent E1 of this comparative example, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0168] The aqueous oxazoline crosslinking agent E1 obtained in this comparative example was diluted in deionized water at a mass ratio of 1:10, resulting in a turbid solution that could not be stored stably, indicating that its water dilution properties were poor.

[0169] Comparative Example 2

[0170] This comparative example provides an aqueous oxazoline crosslinking agent E2, which is prepared by the following process:

[0171] Nitrogen gas was passed through the reaction flask, and 10.0 g of carboxyl polyether G1, 79.5 g of water, and 79.5 g of propylene glycol methyl ether were added. The mixture was heated to 80 °C, and 6.0 g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0 g methyl methacrylate) and olefinic unsaturated monomer (b) (62.0 g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 h. The reaction temperature was maintained at 80 ± 2 °C. After the addition was complete, the mixture was kept at 80 ± 2 °C for another 10 h. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent E2.

[0172] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G1, with a tested acid value of zero, indicating that the carboxyl-containing polyether G1 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G1 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0173] In the oxazoline-containing copolymer, monomer (a) accounts for 28.0 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 60.6 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 11.4 wt% of the oxazoline-containing copolymer.

[0174] The aqueous oxazoline crosslinking agent E2 of this comparative example has a solid content of 40% and an oxazoline equivalent (based on solids) of 194. In the aqueous oxazoline crosslinking agent E2 of this comparative example, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0175] The aqueous oxazoline crosslinking agent E2 obtained in this comparative example was diluted in deionized water at a mass ratio of 1:10, resulting in a turbid solution that could not be stored stably, indicating that its water dilution properties were poor.

[0176] Comparative Example 3

[0177] This comparative example provides an aqueous oxazoline crosslinking agent E3, which is prepared by the following process:

[0178] Nitrogen gas was passed through the reaction flask, and 53.5g of carboxyl polyether G1, 79.5g of water, and 79.5g of propylene glycol methyl ether were added. The mixture was heated to 80°C, and 6.0g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (9.8g of methyl methacrylate) and olefinic unsaturated monomer (b) (36.7g of 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80±2°C. After the addition was complete, the mixture was kept at 80±2°C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent E3.

[0179] In this reaction, the olefinic unsaturated monomer (b) was in excess relative to the carboxyl-containing polyether G1, with a tested acid value of zero, indicating that the carboxyl-containing polyether G1 had completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions occurred simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G1 with the olefinic unsaturated monomer (b) (forming the olefinic unsaturated monomer (c)), as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0180] In the oxazoline-containing copolymer, monomer (a) accounts for 9.8 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 29.1 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c) accounts for 61.1 wt% of the oxazoline-containing copolymer.

[0181] The aqueous oxazoline crosslinking agent E3 of this comparative example has a solid content of 40% and an oxazoline equivalent (based on solids) of 397. In the aqueous oxazoline crosslinking agent E3 of this comparative example, water accounts for 44.3 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0182] The aqueous oxazoline crosslinking agent E3 obtained in this comparative example was diluted in deionized water at a mass ratio of 1:10 to obtain a clear and transparent solution, indicating that it has excellent water dilution properties.

[0183] Comparative Example 4

[0184] This comparative example provides an aqueous oxazoline crosslinking agent E4, which is prepared by the following process:

[0185] (1) Preparation of carboxyl-containing polyether H1:

[0186] Nitrogen gas was introduced into the reaction flask, followed by the addition of 52.0 g tetraethylene glycol monomethyl ether, 39.0 g 2,2,6,6-tetramethylpiperidine oxide (TEMPO, Aladdin Chemical Reagent), and 300.0 g dichloromethane. The mixture was heated to reflux, and dry air was introduced. 15.6 g concentrated nitric acid was added over 15 minutes, and the mixture was then heated to reflux for 17 hours. 150.0 g isopropanol was then added, and the mixture was stirred for 1 hour. Volatile components were removed under vacuum to obtain 50.1 g of the product (i.e., carboxyl-containing resin H1). The acid value was measured to be 253 mg KOH / g, and the calculated carboxyl equivalent was approximately 222.

[0187] Among them, the carboxyl-containing polyether H1 satisfies the general formula (2), and R2 is hydrogen, R3 is methyl, Z is methylene, and the average value of y is... The value is 4, and x is 0.

[0188] (2) Preparation of aqueous oxazoline crosslinking agent E4:

[0189] Nitrogen gas was passed through the reaction flask, and 17.7g of carboxyl polyether H1, 74g of water, and 74g of propylene glycol methyl ether were added. The mixture was heated to 80°C, and 6.0g of 2,2'-azobis(2-amidinepropane) dihydrochloride was added. Monomer (a) (28.0g methyl methacrylate) and olefinic unsaturated monomer (b) (47.0g 2-isopropenyl-2-oxazoline) were mixed evenly and added dropwise to the reaction vessel at a uniform rate over 2 hours. The reaction temperature was maintained at 80±2°C. After the addition was complete, the mixture was kept at 80±2°C for another 10 hours. The acid value was measured to be zero. The resulting pale yellow transparent liquid was the aqueous oxazoline crosslinking agent E4.

[0190] In this reaction, the olefinic unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether H1, with a tested acid value of zero, indicating that the carboxyl-containing polyether H1 has completely reacted with the oxazoline group in the olefinic unsaturated monomer (b). During the reaction, ring-opening reactions (forming olefinic unsaturated monomer (c')) occur simultaneously between monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether H1, as well as polymerization reactions of the unsaturated double bonds (olefin bonds) between the monomers, thus yielding a copolymer containing oxazoline groups.

[0191] In the oxazoline-containing copolymer, monomer (a) accounts for 30.2 wt% of the oxazoline-containing copolymer, olefinic unsaturated monomer (b) accounts for 41.1 wt% of the oxazoline-containing copolymer, and olefinic unsaturated monomer (c') accounts for 28.7 wt% of the oxazoline-containing copolymer.

[0192] The aqueous oxazoline crosslinking agent E4 of this comparative example has a solid content of 40% and an oxazoline equivalent (based on solids) of 287. In the aqueous oxazoline crosslinking agent E4 of this comparative example, water accounts for 44.4 wt% of the total amount of the oxazoline-containing copolymer and water, and organic solvent accounts for 30.7 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

[0193] The aqueous oxazoline crosslinking agent E4 obtained in this comparative example was diluted in deionized water at a mass ratio of 1:10, resulting in a turbid solution that could not be stored stably, indicating that its water dilution properties were poor.

[0194] Example 12

[0195] This embodiment provides an adhesive composition comprising any one of the aqueous oxazoline crosslinking agents D1-D11 from Examples 1-11, and an aqueous polyurethane dispersion (i.e., an aqueous resin containing carboxyl groups), wherein the solids content of the aqueous oxazoline crosslinking agent is 2 parts by weight (if the solids content of the aqueous oxazoline crosslinking agent is 40%, then the amount added to the composition is 2 / 40% = 5 parts), and the weight of the aqueous polyurethane dispersion is 80 parts.

[0196] Example 13

[0197] This embodiment provides an aqueous coating comprising the following components in parts by weight: any one of the aqueous oxazoline crosslinking agents of Examples 1-11; 80 parts of aqueous polyurethane dispersion; 0.2 parts of silicone defoamer; 0.5 parts of silicone leveling agent; 0.5 parts of acetylenic diol wetting defoamer; 1 part of dispersant; 3 parts of matting agent; 6 parts of film-forming aid; 0.5 parts of thickener; and 3.3 parts of water.

[0198] The method for preparing the water-based coating in this embodiment includes the following steps: mixing the components evenly to obtain the water-based coating.

[0199] Example 14

[0200] This embodiment provides an article coated with the water-based coating of Example 13.

[0201] The water-based coatings in Example 13, namely the water-based coatings formed by the water-based oxazoline crosslinking agents in Examples 1-11, were applied to the surface of a PVC substrate to form a coating film with a thickness of 10±2μm on the surface of the PVC substrate.

[0202] Performance testing

[0203] The performance of the aqueous oxazoline crosslinking agents of Examples 1-11 and Comparative Example 3 was tested respectively, and the process is as follows:

[0204] The aqueous oxazoline crosslinking agents D1-D11 and E3 of Examples 1-11 and Comparative Example 3 were respectively formulated into aqueous coatings 1-12 with commercially available aqueous polyurethane dispersion (trade name PU-7012, Guangzhou Guanzhi New Materials, solid content: 35%) according to the formulation in Table 1, and compared with aqueous coating 13 (blank) without the addition of aqueous oxazoline crosslinking agents.

[0205] Table 1. Formulations of Waterborne Coatings

[0206]

[0207]

[0208]

[0209] The following performance tests were conducted on water-based coatings 1-13 respectively:

[0210] Construction and curing conditions: Apply water-based coatings 1-13 to the surface of PVC substrate, bake in a 120℃ forced-air oven for 10 minutes, cool to room temperature to form a coating film with a thickness of 10±2μm, and then conduct performance tests.

[0211] Adhesion test: After applying 3M transparent tape, pull it forcefully and observe how well the coating detaches from the substrate. Rating: 1-5, with 5 being the best (completely no peeling).

[0212] Hot water resistance test: Immerse the coating in boiling water at about 100℃ for 1 minute, and then observe whether the coating turns white or the adhesion decreases. The score is 1-5 points, with 5 points being the best (no whitening of the coating and no significant decrease in adhesion).

[0213] The test results are shown in the table below:

[0214] Table 2 Test Results of Waterborne Coatings

[0215] Water-based coatings Adhesion (Grade) Hot water resistance (points) 1 5 5 2 5 5 3 5 5 4 5 5 5 5 5 6 5 5 7 5 5 8 5 5 9 5 5 10 5 5 11 5 4 12 5 2 13 3 1

[0216] Table 1 shows the waterborne coating formulation, and Table 2 shows the performance test results. The waterborne coating 1-11, which contains the waterborne oxazoline crosslinking agent D1-D11 from Examples 1-11 of this invention, has excellent water dilution properties, adhesion, and hot water resistance.

[0217] The active ingredient in the aqueous oxazoline crosslinking agent E1 of Comparative Example 1, namely the copolymer containing oxazoline groups, does not contain olefinic unsaturated monomers (c) containing polyether groups, resulting in poor water dilution of the aqueous oxazoline crosslinking agent E1 of Comparative Example 1.

[0218] In Comparative Example 2, the effective component of the waterborne oxazoline crosslinking agent E2, namely the copolymer containing oxazoline groups, has a low proportion of olefinic unsaturated monomer (c) in the copolymer containing oxazoline groups, resulting in poor water dilution of the waterborne oxazoline crosslinking agent E2.

[0219] In Comparative Example 3, the effective component of the waterborne oxazoline crosslinking agent E3, namely the copolymer containing oxazoline groups, has an excessively high proportion of olefinic unsaturated monomer (c) in the copolymer containing oxazoline groups, resulting in high hydrophilicity of the copolymer itself. After the waterborne oxazoline crosslinking agent E3 of Comparative Example 3 is formulated into waterborne coating 12, its hot water resistance is poor, which affects the hot water resistance performance of the coating film.

[0220] In Comparative Example 4, the effective component of the waterborne oxazoline crosslinking agent E4, namely the copolymer containing oxazoline groups, has a low y value, resulting in poor water dilution of the waterborne oxazoline crosslinking agent E4.

[0221] The water-based coating 13 without the addition of a water-based crosslinking agent has poor adhesion and hot water resistance.

[0222] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A copolymer containing an oxazoline group, characterized in that: Include: a) at least one monomer selected from C1-20 alkyl esters of (meth)acrylate and C8-20 vinyl aromatic compounds; b) at least one olefinic unsaturated monomer (b), said olefinic unsaturated monomer (b) comprising an oxazoline group; c) at least one olefinically unsaturated monomer (c), said olefinically unsaturated monomer (c) comprising a polyether group, and said olefinically unsaturated monomer (c) having a structure of at least one of formula (1): In formula (1), R1 and R2 are each independently hydrogen or methyl; R3 is a hydrocarbon group with 1-8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1-8 carbon atoms; x is 0 or 1; y is 6-68; In the oxazoline-containing copolymer, the monomer (a) accounts for 0-40 wt% of the oxazoline-containing copolymer, the olefinic unsaturated monomer (b) accounts for 38-70 wt% of the oxazoline-containing copolymer, and the olefinic unsaturated monomer (c) accounts for 15-50 wt% of the oxazoline-containing copolymer.

2. The copolymer containing an oxazoline group according to claim 1, characterized in that: The olefinically unsaturated monomer (c) is obtained by reacting the carboxyl-containing polyether G with the olefinically unsaturated monomer (b); the structure of the carboxyl-containing polyether G is at least one of formula (2): In formula (2), R2 is hydrogen or methyl; R3 is a hydrocarbon group with 1 to 8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1 to 8 carbon atoms; x is 0 or 1; y is 6-68.

3. A method for preparing an oxazoline-containing copolymer as described in any one of claims 1-2, characterized in that: Includes the following steps: The monomer (a), the olefinically unsaturated monomer (b), and the olefinically unsaturated monomer (c) are polymerized to obtain the product.

4. A method for preparing an oxazoline-containing copolymer as described in any one of claims 1-2, characterized in that: Includes the following steps: The product is prepared by reacting the monomer (a), the olefinic unsaturated monomer (b), and the carboxyl-containing polyether G, wherein the olefinic unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether G. During the reaction, the ring-opening reaction between the carboxyl-containing polyether G and the olefinic unsaturated monomer (b) and the polymerization reaction of the unsaturated double bonds of each monomer occur. The structure of the carboxyl-containing polyether G is at least one of formula (2): In formula (2), R2 is hydrogen or methyl; R3 is a hydrocarbon group with 1 to 8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1 to 8 carbon atoms; x is 0 or 1; y is 6-68.

5. An aqueous oxazoline crosslinking agent, characterized in that: Includes the oxazoline-containing copolymer as described in any one of claims 1-2 and water, wherein water accounts for 30-90 wt% of the total amount of the oxazoline-containing copolymer and water.

6. The aqueous oxazoline crosslinking agent according to claim 5, characterized in that: It also includes an organic solvent, which accounts for 5-50 wt% of the total amount of the oxazoline-containing copolymer, water, and organic solvent.

7. A method for preparing an aqueous oxazoline crosslinking agent as described in any one of claims 5-6, characterized in that: Includes the following steps: Water or water and an organic solvent are added to a reaction vessel, along with an initiator. The mixture is heated to 50-90°C, and then a mixture of the monomer (a), the olefinically unsaturated monomer (b), and the olefinically unsaturated monomer (c) is added to the reaction vessel to carry out the reaction, ultimately yielding the aqueous oxazoline crosslinking agent.

8. A method for preparing an aqueous oxazoline crosslinking agent as described in any one of claims 5-6, characterized in that: Includes the following steps: The carboxyl-containing polyether G is added to a container, water or water and an organic solvent are added, and an initiator is added. The mixture is heated to 50-90°C, and a mixture of the monomer (a) and the olefinic unsaturated monomer (b) is added to the reaction vessel for reaction, wherein the olefinic unsaturated monomer (b) is in excess relative to the carboxyl-containing polyether G, and the aqueous oxazoline crosslinking agent is finally obtained. The structure of the carboxyl-containing polyether G is at least one of formula (2): In formula (2), R2 is hydrogen or methyl; R3 is a hydrocarbon group with 1 to 8 carbon atoms; Z is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group with 1 to 8 carbon atoms; x is 0 or 1; y is 6-68.

9. A water-based coating, ink, or adhesive composition, characterized in that: It includes the aqueous oxazoline crosslinking agent as described in any one of claims 5-6 and the carboxyl-containing aqueous resin, wherein the aqueous oxazoline crosslinking agent is 2-10 wt% of the carboxyl-containing aqueous resin.

10. An article coated with the water-based paint, ink, or adhesive composition as described in claim 9.

Images