CN110128875B

CN110128875B - Novel self-crosslinking emulsion of water-based ink binder for flexographic printing and preparation method thereof

Info

Publication number: CN110128875B
Application number: CN201910422326.6A
Authority: CN
Inventors: 李效玉; 王海侨; 张泽琪; 刘亚男; 叶壮志; 赵鹏飞
Original assignee: China Academy Of Printing Technology Co ltd; Beijing University of Chemical Technology
Current assignee: China Academy Of Printing Technology Co ltd; Beijing University of Chemical Technology
Priority date: 2019-05-21
Filing date: 2019-05-21
Publication date: 2020-09-11
Anticipated expiration: 2039-05-21
Also published as: CN110128875A

Abstract

The invention discloses a novel self-crosslinking emulsion of a water-based ink binder for flexographic printing and a preparation method thereof, wherein the novel self-crosslinking emulsion of the water-based ink binder for flexographic printing is a copolymer emulsion prepared by emulsion copolymerization of the following components: 30-70 parts of deionized water, 5-35 parts of water-based resin, 2-40 parts of alkyl acrylate monomer with 4-12 total carbon atoms, 0-25 parts of methacrylate monomer with 5-20 total carbon atoms, 0-25 parts of styrene monomer, 0.2-5 parts of (methyl) hydroxy acrylate monomer, 0.5-5 parts of crosslinking monomer, 0.01-0.5 part of metal ion crosslinking agent, 0.01-0.1 part of initiator and 0-10 parts of pH regulator. The self-crosslinking emulsion of the novel water-based ink binder for flexographic printing can perform self-crosslinking reaction at room temperature, and has excellent redissolution property, water resistance and printing transfer property.

Description

Novel self-crosslinking emulsion of water-based ink binder for flexographic printing and preparation method thereof

Technical Field

The invention relates to the technical field of aqueous resin and synthesis thereof, in particular to a novel self-crosslinking emulsion of an aqueous ink binder for flexographic printing and a preparation method thereof.

Background

In recent years, with the increasing importance on air pollution and environmental protection, the traditional packaging and printing industry with high VOC emission is under great transformation pressure, so the status of flexible printing and water-based ink is gradually improved. Acrylic emulsions are popular in the printing industry as aqueous ink vehicles because of their advantages such as simple synthesis, high molecular weight, weatherability, oil resistance, and high gloss. However, the conventional acrylic emulsion prepared by using the small molecular emulsifier has some disadvantages such as poor printing transferability, insufficient adhesion to non-absorbent substrates, poor re-solubility, slow drying speed, easy migration of the small molecular emulsifier to the surface of the ink, resulting in poor water resistance, and the like, and cannot meet the requirements of the flexo printing technology. The aqueous resin is generally a random copolymer of a hydrophobic monomer (e.g., methyl methacrylate, butyl acrylate, styrene, etc.) and a monomer containing a carboxylic acid group (e.g., acrylic acid, methacrylic acid, etc.). The water-based resin is taken as a macromolecular emulsifier, so that the problems of a series of micromolecular emulsifiers can be solved. Acrylic emulsions prepared using aqueous resins as emulsifiers have many advantages such as newton's rheological behavior, excellent freeze-thaw characteristics and stability, good pigment dispersion, good wetting, ease of printer cleaning, good re-solubility, etc.

In the development process of the flexographic printing water-based ink vehicle at the present stage, a plurality of defects still exist. Patent publication No. CN 102911559A discloses "an anti-sticking pure acrylic emulsion for water-based ink", which uses self-made water-based resin as protective colloid and different acrylate monomers as comonomers to prepare pure acrylic emulsion. However, the small molecular emulsifier used in the preparation of the aqueous resin is brought into the process of synthesizing the emulsion, so that the prepared emulsion still contains more small molecular emulsifier, which causes poor water resistance of the emulsion and influences the surface property of the emulsion. In addition, when an acrylic emulsion is prepared by using an aqueous resin, the molecular weight and molecular weight distribution of the aqueous resin, acid value, glass transition temperature and other parameters have a great influence on the performance of the emulsion, and therefore, these parameters are required to be very strict, and in particular, the molecular weight distribution is required to be as narrow as possible. Obviously, the aqueous resin prepared by the conventional method does not have the characteristics, so that the aqueous resin cannot be really applied to the wide industrialization. In addition, the method does not use any crosslinking monomer, and a large number of hydrophilic groups such as carboxyl and the like exist in an emulsion system, so that the adhesive film has poor mechanical properties, poor water resistance and medium resistance, and cannot meet the performance requirements of high-quality ink.

Patent publication No. CN 101717463A discloses a water-soluble ink binder resin for plastics and a preparation method thereof, styrene and different acrylate monomers are used as comonomers to prepare a styrene-acrylic emulsion which can be infinitely dissolved in water and has no pungent smell. However, the publication does not mention re-solubility of the emulsion, and the VOC emission is high due to the addition of a large amount of the alcohol solvent.

Patent publication No. CN 104789041A discloses a zirconium chelate complex modified composite alkali-soluble emulsion, high-redissolution water-based ink prepared from the zirconium chelate complex modified composite alkali-soluble emulsion and a method for preparing the high-redissolution water-based ink. However, the method belongs to the traditional acrylic emulsion prepared by using a small molecular emulsifier, and the corresponding ink has the defect of poor printing transfer property, cannot meet the requirements of high-speed flexo printing technology, and uses solvents such as ethanol, isopropanol and the like.

Disclosure of Invention

The invention aims to provide a novel self-crosslinking emulsion of a water-based ink binder for flexographic printing, which has excellent re-solubility, water resistance and printing transfer property, and a preparation method thereof.

The technical scheme of the invention is as follows:

the novel self-crosslinking emulsion of the water-based ink vehicle for flexographic printing is a copolymer emulsion prepared by emulsion copolymerization of the following components: 30-70 parts of deionized water, 5-35 parts of water-based resin, 2-40 parts of alkyl acrylate monomer with the total carbon number of 4-12, 0-40 parts of methacrylate monomer with the total carbon number of 5-20, 0-20 parts of styrene monomer, 0.2-5 parts of (methyl) hydroxy acrylate monomer, 0.5-5 parts of crosslinking monomer, 0.01-0.5 part of metal ion crosslinking agent, 0.1-2 parts of initiator and 0-10 parts of pH regulator.

The water-based resin is a random copolymer of a hydrophobic monomer containing a carbon-carbon double bond and a monomer containing a carboxyl group and the carbon-carbon double bond, the hydrophobic monomer is one or more of methyl methacrylate, ethyl acrylate, butyl acrylate and styrene, the monomer containing the carboxylic acid group is one or more of acrylic acid, methacrylic acid and maleic acid, and the random copolymer is obtained by bulk or solution polymerization, the number average molecular weight of the water-based resin is 2000-15000, the acid value is 50-300, and the glass transition temperature is 20-150 ℃.

The acrylic acid alkyl ester monomer with the total carbon number of 4-12 is one or more of methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, isooctyl acrylate and isobornyl acrylate. Among them, one or more of butyl acrylate, isooctyl acrylate and isobornyl acrylate are preferable.

The methacrylate monomer with the total carbon number of 5-20 is one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobornyl methacrylate, dodecyl methacrylate and octadecyl methacrylate.

The hydroxyl (methyl) acrylate is hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate or hydroxypropyl methacrylate.

The crosslinking monomer is one or more of glycidyl methacrylate, (meth) acrylamide, hydroxymethyl acrylamide, hydroxyethyl acrylamide and DAAM/ADH.

The metal ion crosslinking agent is one or more of zinc ion complex, zirconium ion complex, calcium ion complex, magnesium ion complex and chromium ion complex.

The initiator is one or more of potassium persulfate, ammonium persulfate and sodium persulfate.

The pH regulator is one or more of potassium hydroxide, sodium hydroxide, ammonia water, AMP-95, triethylamine, ethylenediamine and triethanolamine. Wherein, the preferred composition is three compositions of sodium hydroxide, ammonia water and AMP-95.

The preparation method of the novel self-crosslinking emulsion of the water-based ink binder for flexographic printing comprises the following steps:

(1) preparing materials: the raw materials were prepared according to the following formula: 30-70 parts of deionized water, 5-35 parts of water-based resin, 2-40 parts of alkyl acrylate monomer with the total carbon number of 4-12, 0-40 parts of methacrylate monomer with the total carbon number of 5-20, 0-20 parts of styrene monomer, 0.2-5 parts of (methyl) hydroxy acrylate monomer, 0.5-5 parts of crosslinking monomer, 0.1-2 parts of initiator and 0-10 parts of pH regulator;

(2) dissolving the water-based resin: adding the weighed water-based resin and part of deionized water in the step (1) into a reactor provided with a reflux condenser tube, a thermometer, a stirring paddle and a nitrogen inlet tube, adding a pH regulator into the reactor under mechanical stirring, and continuously stirring the mixture for 30 to 90 minutes at the temperature of between 70 and 100 ℃ to obtain a water-based resin solution;

(3) preparing a seed emulsion: adding 4 wt% of alkyl acrylate monomer with the total carbon number of 4-12, methacrylate unsaturated monomer with the total carbon number of 4-20, styrene monomer, hydroxyl (meth) acrylate monomer and crosslinking monomer weighed in the step (1) and the rest of deionized water into the aqueous resin solution prepared in the step (2), continuously stirring for 20-40 minutes, adding 50 wt% of initiator, and keeping the temperature at 80-85 ℃ for 20-40 minutes under the condition of continuous stirring to obtain seed emulsion;

(4) preparing an emulsion: and (3) dropwise adding the rest alkyl acrylate monomer with the total carbon number of 4-12, the methacrylate unsaturated monomer with the total carbon number of 5-20, the styrene monomer, the (methyl) hydroxy acrylate monomer, the crosslinking monomer and the initiator into the seed emulsion prepared in the step (3) within 60-180 minutes, controlling the reaction temperature at 70-90 ℃, and preserving the heat for 90-180 minutes.

(5) Addition of a crosslinking agent: reducing the reaction temperature to 65-75 ℃, adjusting the pH value of the reaction solution to 7-9 by using a pH regulator, adding a metal cross-linking agent, keeping the temperature for 20-40 minutes, reducing the temperature to room temperature, adding adipic dihydrazide, continuously stirring for 30-40 minutes, and filtering to obtain an emulsion, namely the novel self-crosslinking emulsion for the water-based ink binder for flexographic printing.

The invention has the advantages and beneficial effects that:

1. the invention uses the water resin as the emulsifier to endow the ink with excellent re-solubility and printing transfer property; no small molecular emulsifier is used, and a monomer which can generate crosslinking reaction at room temperature is introduced, so that the water resistance of the ink is improved; the particle size of the emulsion is controlled below 100nm to ensure that the emulsion has ideal drying speed and excellent film-forming property; the high glossiness and the dispersibility to color paste are endowed to the ink by using a compounding technology of the water-based resin with large molecular weight and small molecular weight. The multiple composite crosslinking system endows the ink with excellent mechanical property and medium resistance, and simultaneously solves the problem that the redissolution property, the mechanical property and the medium resistance of the water-based ink cannot be well balanced by utilizing the difference of crosslinking reaction speeds of different crosslinking systems. The water-based ink resin binder prepared by the invention has the advantages of simple process, low cost, excellent performance and high application value.

2. The self-crosslinking acrylate emulsion has the advantages of simple production process, safety, environmental protection and low cost, and the water-based ink with good stability, high glossiness, strong water resistance, excellent redissolution property and printing transfer property can be obtained by applying the prepared acrylate emulsion to the flexographic printing industry. The adhesive has excellent adhesive force when being applied to PP ink, PE films and pure white PE films. Has wide application prospect in the aspect of high-end product packaging.

Detailed Description

[ example 1]

Dissolving of the aqueous resin: at the temperature of 80 ℃, the rotating speed of 300r/min, under the nitrogen atmosphere, 140g of waterborne resin with the molecular weight of 7000, 656.3g of deionized water and 43.7g of ammonia water with the mass concentration of 25 percent are sequentially added into a 2L reaction kettle, and the pure and transparent waterborne resin solution is obtained after 30-40min stirring.

Preparing a monomer mixed solution: 112.4g of styrene, 112.4g of methyl methacrylate, 87.6g of butyl acrylate, 87.6g of isooctyl acrylate, 8g of isobornyl acrylate, 8g of hydroxyethyl acrylate, 12g of diacetone acrylamide and 2g of glycidyl methacrylate are uniformly mixed to obtain a yellow transparent solution.

And (3) taking 4 wt% of the prepared yellow transparent solution at the temperature of 86-88 ℃ and the rotating speed of 300r/min under the nitrogen atmosphere, adding the yellow transparent solution into the dissolved water-based resin, and simultaneously adding 2g of sodium persulfate to obtain the blue seed emulsion.

The remaining monomer solution was added dropwise to the system while controlling the addition time to one hour, and 1.2g of an aqueous sodium persulfate solution was added dropwise over a slightly longer period than the monomer addition time. After the dropwise addition, the mixture was cured at 88 ℃ for 2 hours.

And (2) reducing the reaction temperature to 70 ℃, adding 60g of AMP-95 aqueous solution into the system, adding 8g of zinc acetate solution with the mass concentration of 25%, curing for 30 minutes at 70 ℃, reducing the temperature to room temperature, adding 6g of adipic dihydrazide, continuously stirring for 30 minutes, filtering and discharging by using a 200-mesh filter screen to obtain milky emulsion, namely the emulsion for the flexographic printing water-based ink binder.

[ example 2]

Dissolving of the aqueous resin: at the temperature of 80 ℃, the rotating speed of 300r/min, under the nitrogen atmosphere, 140g of 7000 aqueous resin, 356.3g of deionized water and 43.7g of ammonia water with the mass concentration of 25% are sequentially added into a 2L reaction kettle, and the pure and transparent aqueous resin solution is obtained after 30-40min of stirring.

Preparing a pre-emulsion, namely adding 303.7g of deionized water and 100g of aqueous resin solution into the monomer mixed solution, and magnetically stirring for 30 minutes to obtain a white pre-emulsion.

The remaining 440g of aqueous resin solution was added to the reactor, and 1.5g of sodium persulfate was added thereto at 88 ℃ and 1.2g of the pre-emulsion and the aqueous solution of sodium persulfate were added dropwise over one hour. After the completion of the dropwise addition, the mixture was aged at 88 ℃ for 2 hours.

[ example 3]

Preparing a monomer mixed solution: 112.4g of styrene, 112.4g of methyl methacrylate, 87.6g of butyl acrylate, 87.6g of isooctyl acrylate, 8g of isobornyl acrylate, 8g of hydroxyethyl acrylate, 12g of diacetone acrylamide and 2g of glycidyl methacrylate are uniformly mixed to obtain a yellow transparent solution

Preparing a fine emulsion: 303.7g of deionized water and 100g of aqueous resin solution are added into the monomer mixed solution, 2g of octadecyl acrylate is added, and the mixture is dispersed for 10min by using a cell crusher to obtain white fine emulsion.

The remaining 440g of the aqueous resin solution was added to the reaction vessel, and 1.5g of sodium persulfate was added thereto at a reaction temperature of 88 ℃ and the fine emulsion and 1.2g of the aqueous sodium persulfate solution were added dropwise over one hour after completion of the dropwise addition. Aging at 88 deg.C for 2 hr.

[ example 4]

In the preparation of the aqueous ink vehicle emulsion, 140g of 7000 aqueous resin, 656.3g of deionized water and 43.7g of 25% ammonia water are replaced by 70g of 7000 aqueous resin, 616.2g of deionized water and 21.8g of 25% ammonia water. Otherwise the same as in example 1

[ example 5]

In the preparation of the aqueous ink vehicle emulsion, 140g of 7000 aqueous resin, 656.3g of deionized water and 43.7g of 25% ammonia water are replaced by 280g of 7000 aqueous resin, 726.6g of deionized water and 87.4g of 25% ammonia water. Otherwise the same as in example 1

[ example 6]

In the preparation of the aqueous ink vehicle emulsion, 140g of the aqueous resin with the molecular weight of 7000 is changed into 140g of the aqueous resin with the molecular weight of 8600. The rest is the same as in example 1.

[ example 7]

In the preparation of the aqueous ink vehicle emulsion, 140g of the aqueous resin with the molecular weight of 7000 is changed into 140g of the aqueous resin with the molecular weight of 12000. The rest is the same as in example 1.

[ example 8]

In the preparation of the aqueous ink vehicle emulsion, 140g of the aqueous resin with the molecular weight of 7000 is changed into 60g of the aqueous resin with the molecular weight of 2000 and 80g of the aqueous resin with the molecular weight of 12000. The rest is the same as in example 1.

[ example 9]

In the method, 43.7g of 25% ammonia water by mass was changed to 31.67g of AMP-95 in the preparation of the aqueous ink vehicle emulsion. The rest is the same as in example 1.

[ example 10]

In the preparation of the aqueous ink vehicle emulsion, 43.7g of 25% ammonia water was changed to 15.83g of AMP-95 and 21.85g of 25% ammonia water. The rest is the same as in example 1.

[ example 11]

In the preparation of the aqueous ink vehicle emulsion, 43.7g of 25% ammonia water by mass was changed to 6.33g of AMP-95, 17.48g of 25% ammonia water by mass, and 10.31g of NaOH. The rest is the same as in example 1.

[ example 12]

In the method, 2g of glycidyl methacrylate is changed into 4g of cross-linking monomer acrylamide in the preparation of the aqueous ink vehicle emulsion. The rest is the same as in example 1.

[ example 13]

In the method, 2g of glycidyl methacrylate is changed into 4g of hydroxymethyl acrylamide in the preparation of the aqueous ink vehicle emulsion. The rest is the same as in example 1.

[ example 14]

In the preparation of the aqueous ink vehicle emulsion, 8g of hydroxyethyl acrylate is replaced by 8g of hydroxypropyl acrylate. The rest is the same as in example 1.

[ example 15]

According to the implementation method, sodium persulfate is replaced by ammonium persulfate in the preparation of the aqueous ink vehicle emulsion. The rest is the same as in example 1.

[ example 16]

According to the implementation method, sodium persulfate is completely replaced by potassium persulfate in the preparation of the aqueous ink vehicle emulsion. The rest is the same as in example 1.

[ example 17]

In the preparation of the aqueous ink vehicle emulsion, 8g of a 25% by mass zinc acetate solution was changed to 4g of a zirconium ion complex Tyzor 212. Otherwise the same as in example 1

[ comparative example ]

Preparing a monomer mixed solution: 112.4g of styrene, 112.4g of methyl methacrylate, 87.6g of butyl acrylate, 87.6g of isooctyl acrylate, 8g of isobornyl acrylate and 8g of hydroxyethyl acrylate are uniformly mixed to obtain a yellow transparent solution.

The remaining monomer solution was added dropwise to the system while controlling the addition time to one hour, and 1.2g of an aqueous sodium persulfate solution was added dropwise over a slightly longer period than the monomer addition time. After the dropwise addition, curing for 2 hours at 88 ℃, cooling to room temperature, adding 60g of AMP-95 aqueous solution into the system, filtering and discharging by using a 200-mesh filter screen to obtain milky emulsion, namely the emulsion for the flexographic printing water-based ink binder.

TABLE I comparison of emulsion stocks of the examples of the invention

In the table, the particle size is measured by using a NanoZS nanometer particle size tester, the test temperature is 25 ℃, and the average value is obtained by measuring three times, so that the particle size and the particle size distribution of the latex particles in the emulsion are obtained.

And measuring the crosslinking degree in the table by adopting an acetone soaking method, soaking the latex film in acetone for 24 hours, and calculating the change of the mass before and after the soaking for 24 hours to obtain the crosslinking degree of the latex film.

In the meter, a viscosity meter of an observation cup is used for measuring the viscosity, the viscosity meter is filled with the glue solution, then the glue solution flows out, a stopwatch is started at the same time until the flowing thread of the glue solution is interrupted, the stopwatch is stopped, the time is the conditional viscosity of the glue solution, the measurement is repeated once, and the error is not more than 3 percent of the average value.

The invention is applied to the flexographic printing water-based ink, and the experimental data of the performance of each embodiment are compared as follows:

simple water-based ink formula

Resin binder	Color paste	Wetting and leveling agent	Defoaming agent	Wear-resistant auxiliary
					50％	40％	1％	1％	8％

TABLE III comparison of the Performance of the films produced on the BOPP/PE film substrate by using a proofing machine

The adhesive force in the above table is determined by taking a section of ink sample strip (about 10cm long), sticking an ink film with a certain area with a 3M600 adhesive tape, flattening, rapidly removing the adhesive tape, repeating for three times, observing the condition that the ink film is stuck off by the adhesive tape, and determining grades according to the number of sticking-off, including excellent, good, medium and poor.

The water resistance in the above table was determined by cutting a small sample of the ink prepared and immersing it in water. After 24h, the film is taken out to observe whether the deionized water is discolored or not and whether the coating film is peeled off or not, and the grades are determined according to the number of discolored and peeled off, namely, excellent, good, medium and poor.

The anti-blocking determination method in the above table is to fold and contact the prepared ink sample strips once within 30 minutes, press the ink sample strips under a weight of 2KG in an oven at 50 ℃, place the ink sample strips for 2 hours, and determine the grade according to the blocking condition of the prints and the excellent, good, medium and poor prints from few to many.

The re-solubility in the above table is determined by coating a layer of ink on a glass substrate, dropping a drop of water after the ink is initially dried, observing the ink dissolution, and determining the grade according to the number of times of dissolution, including excellent, good, medium and poor.

From the above results, it was confirmed that a novel self-crosslinking emulsion for an aqueous ink vehicle for flexographic printing having excellent re-solubility, water resistance and printing transfer properties, which has a small particle size, high stability and good adhesion can be obtained by using the styrene-acrylic emulsion designed according to the present invention.

Industrial applicability

The invention can prepare the acrylate emulsion with simple production process, safety, environmental protection and low cost, and the water-based ink with good stability, high glossiness, strong water resistance, excellent redissolution property and printing transfer property can be obtained by applying the prepared acrylate emulsion to the flexographic printing industry. The adhesive has excellent adhesive force when being applied to PP ink, PE films and pure white PE films. Has wide application prospect in the aspects of high-end food packaging and the like.

The embodiments of the present invention are not exhaustive, and those skilled in the art can select them from the prior art.

The above disclosure is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and shall be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the above claims.

Claims

1. A novel self-crosslinking emulsion of a water-based ink binder for flexographic printing is characterized in that the emulsion is a copolymer emulsion prepared by emulsion copolymerization of the following components: 30-70 parts of deionized water, 5-35 parts of water-based resin, 2-40 parts of alkyl acrylate monomer with the total carbon number of 4-12, 0-25 parts of methacrylate monomer with the total carbon number of 5-20, 0-25 parts of styrene monomer, 0.2-5 parts of (methyl) hydroxy acrylate monomer, 0.5-5 parts of crosslinking monomer, 0.01-0.5 part of metal ion crosslinking agent, 0.01-0.1 part of initiator and 0-10 parts of pH regulator; the water-based resin is a random copolymer of a hydrophobic monomer containing a carbon-carbon double bond and a carboxyl group, the number average molecular weight of the water-based resin is 2000-15000, the acid value is 50-300, and the glass transition temperature is 20-150 ℃; the crosslinking monomer is a composition of a component A and a component B, the component A is DAAM or a mixture of DAAM and one or more of glycidyl methacrylate, (meth) acrylamide, hydroxymethyl acrylamide and hydroxyethyl acrylamide, and the component B is ADH; the preparation method of the novel self-crosslinking emulsion of the water-based ink binder for flexographic printing comprises the following steps:

(1) preparing materials: the raw materials were prepared according to the following formula: 30-70 parts of deionized water, 5-35 parts of water-based resin, 2-40 parts of alkyl acrylate monomer with the total carbon number of 4-12, 0-25 parts of methacrylate monomer with the total carbon number of 5-20, 0-25 parts of styrene monomer, 0.2-5 parts of (methyl) hydroxy acrylate monomer, 0.5-5 parts of crosslinking monomer, 0.01-0.5 part of metal ion crosslinking agent, 0.01-0.1 part of initiator and 0-10 parts of pH regulator;

(3) preparing a seed emulsion: adding 4 wt% of the alkyl acrylate monomer with the total carbon number of 4-12, the methacrylate unsaturated monomer with the total carbon number of 5-20, the styrene monomer, the hydroxyl (meth) acrylate monomer and the component A weighed in the step (1) and the rest of deionized water into the aqueous resin solution prepared in the step (2), continuously stirring for 20-40 minutes, adding 50 wt% of an initiator, and keeping the temperature at 80-85 ℃ for 20-40 minutes under the condition of continuous stirring to obtain a seed emulsion;

(4) preparing an emulsion: dropwise adding the rest alkyl acrylate monomer with the total carbon number of 4-12, the rest methacrylate unsaturated monomer with the total carbon number of 5-20, the rest styrene monomer, the rest hydroxyl (meth) acrylate monomer, the component A and the rest initiator into the seed emulsion prepared in the step (3) within 60-180 minutes, controlling the reaction temperature at 70-90 ℃, and preserving the heat for 90-180 minutes;

2. The novel self-crosslinking emulsion for an aqueous ink vehicle for flexographic printing according to claim 1 wherein the hydrophobic monomer is one or more of methyl methacrylate, ethyl acrylate, butyl acrylate and styrene and the carboxylic acid group containing monomer is one or more of acrylic acid, methacrylic acid and maleic acid.

3. The novel self-crosslinking emulsion for an aqueous ink vehicle for flexographic printing according to claim 1 or2, wherein the alkyl acrylate monomer having a total carbon number of 4 to 12 is one or more of methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, isooctyl acrylate, and isobornyl acrylate.

4. The novel self-crosslinking emulsion for the aqueous ink vehicle for flexographic printing according to claim 1 or2, wherein the methacrylate monomer having a total carbon number of 5 to 20 is one or more selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobornyl methacrylate, dodecyl methacrylate and octadecyl methacrylate.

5. The novel self-crosslinking emulsion for aqueous ink vehicles for flexographic printing according to claim 1 or2 wherein the hydroxy (meth) acrylate is one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.

6. The novel self-crosslinking emulsion for aqueous ink vehicles for flexographic printing according to claim 1 or2, characterized in that the metal ion crosslinking agent is one or more of zinc ion complex, zirconium ion complex, calcium ion complex, magnesium ion complex and chromium ion complex.

7. The novel self-crosslinking emulsion for aqueous flexographic printing ink vehicles according to claim 1 or2, characterized in that the initiator is one or more of potassium persulfate, ammonium persulfate and sodium persulfate.

8. The novel self-crosslinking emulsion for aqueous ink vehicles for flexographic printing according to claim 1 or2 wherein the pH adjusting agent is one or more of potassium hydroxide, sodium hydroxide, ammonia, AMP-95, triethylamine, ethylenediamine and triethanolamine.

9. The method for preparing the novel self-crosslinking emulsion of the water-based ink vehicle for flexographic printing according to any one of claims 1 to 8, comprising the steps of:

(1) preparing materials: the raw materials were prepared according to the following formula: 30-70 parts of deionized water, 5-35 parts of water-based resin, 2-40 parts of alkyl acrylate monomer with the total carbon number of 4-12, 0-25 parts of methacrylate monomer with the total carbon number of 5-20, 0-25 parts of styrene monomer, 0.2-5 parts of (methyl) hydroxy acrylate monomer, 0.5-5 parts of crosslinking monomer, 0.01-0.5 part of metal ion crosslinking agent, 0.01-0.1 part of initiator and 0-10 parts of pH regulator; the crosslinking monomer is a composition of a component A and a component B, the component A is DAAM or a mixture of DAAM and one or more of glycidyl methacrylate, (meth) acrylamide, hydroxymethyl acrylamide and hydroxyethyl acrylamide, and the component B is ADH;