Three-peak distribution high-solid-content water-based acrylic pressure-sensitive adhesive emulsion and preparation method thereof

Abstract

The invention relates to the technical field of acrylic pressure-sensitive adhesives, in particular to a three-peak distribution high-solid-content water-based acrylic pressure-sensitive adhesive emulsion and a preparation method thereof. The water-based acrylic pressure-sensitive adhesive emulsion comprises the following components in parts by weight: 10-30 parts of a polymer A and 70-90 parts of a polymer B, the polymer A is an acrylic emulsion with unimodal distribution at a position of 100-200 nm, and the polymer B is an acrylic emulsion with bimodal distribution at a position of 40-80 nm and a position of 300-800 nm. The polymer A and the polymer B are matched according to a certain proportion to obtain a unique three-peak distribution water-based pressure-sensitive adhesive emulsion, and latex particles of the polymer A can further fill gaps of latex particles of the polymer B so as to realize high solid content and low viscosity.

Description

Technical Field

[0001] The present invention relates to the technical field of acrylic pressure-sensitive adhesives, and particularly relates to a water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution and high solid content and a preparation method thereof. Background Art

[0002] Water-based acrylate pressure-sensitive adhesives are gradually replacing solvent-based acrylate pressure-sensitive adhesives due to their environmental protection, safety, and low odor advantages. However, traditional water-based acrylic pressure-sensitive adhesive emulsions have a low solid content and require more time and energy to dry, which no longer meets the requirements of modern assembly line production. When the solid content of the emulsion prepared by the conventional emulsion polymerization method exceeds 50%, the viscosity will increase sharply with the increase of the solid content, and it will bring problems of system stability and heat transfer and dissipation.

[0003] Chinese Patent Invention No. CN110105489A discloses a production method of a high-solid-content and ultra-high-molecular-weight acrylate copolymer emulsion. By introducing an emulsifier, a wetting agent, an emulsifying dispersant, and a pH regulator into the emulsion polymerization of acrylate mixed monomers, an acrylate copolymer emulsion with a high solid content (50-55%) and a high molecular weight (Mw = 9.5 million - 10.5 million) is prepared. However, this production method uses too many dispersants, emulsifiers, and wetting agents, which has an adverse effect on the water white resistance of the emulsion, and the final solid content of the emulsion is still not higher than 55%.

[0004] Chinese Patent Invention No. CN113549415A discloses a high-solid-content peelable water-based pressure-sensitive adhesive and a preparation method thereof. Its raw materials include 5-15 parts of hard monomers, 60-90 parts of soft monomers, 2-4 parts of a compound emulsifier containing reactive and non-reactive components, 3-8 parts of functional monomers, 0.2-2 parts of internal cross-linking monomers, etc. Such high-solid-content peelable water-based pressure-sensitive adhesives have the advantages of good three-force performance, water white resistance, peelability, and good low-temperature initial tack, but their emulsion viscosity is too high (both ≥4000 mPa·s), which is not conducive to construction operations.

[0005] Chinese Patent Invention No. CN109134743A discloses a preparation method of a high-solid-content and low-viscosity acrylic pressure-sensitive adhesive. By continuously and uniformly dropping a pre-emulsion and seeds during the polymerization process, new latex particles are continuously formed during the polymerization process, thereby achieving high solid content and low viscosity. However, the seeds used in this method are taken from the seed emulsion in the seeding stage, and this seed emulsion has not experienced a complete emulsion polymerization process, has a large amount of residual monomers, and poor stability, resulting in poor batch-to-batch repeatability and poor product performance stability. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution and high solid content and good stability and a preparation method thereof.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: a water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution and high solid content, by weight, includes 10 to 30 parts of polymer A and 70 to 90 parts of polymer B; The polymer A is an acrylic emulsion with a single-peak distribution at 100 to 200 nm and a ketone carbonyl group on the surface, and the polymer B is an acrylic emulsion with a double-peak distribution at 40 to 80 nm and 300 to 800 nm and a hydrazide group on the surface.

[0008] Another technical solution adopted by the present invention is: a preparation method of the above-mentioned water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution and high solid content, including the following steps: adding polymer B, stirring and dropwise adding polymer A, adding an antifoaming agent and a bactericide, mixing evenly and filtering to obtain a water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution and high solid content.

[0009] The beneficial effects of the present invention are as follows: the present invention can obtain a unique water-based pressure-sensitive adhesive emulsion with a three-peak distribution by matching polymer A and polymer B in a certain proportion. The latex particles of polymer A can further fill the gaps between the latex particles of polymer B, thereby achieving a high solid content (≥62%) and a low viscosity (≤800 mPa·s).

[0010] At the same time, the ketone carbonyl group on the surface of polymer A and the hydrazide group on the surface of polymer B can promote the fusion between the two latex particles and greatly reduce the gap between the particles through the "hydrazide crosslinking" reaction, thereby improving water resistance and other properties. The pressure-sensitive adhesive emulsion of the present invention has excellent initial adhesion performance and excellent "three-force balance" without adding a tackifying resin. Description of the Drawings

[0011] Figure 1 It is the particle size distribution diagram of the pressure-sensitive adhesive emulsion of Example Sample 1. Detailed Embodiments

[0012] To illustrate the technical content, the achieved objectives and effects of the present invention in detail, the following is described in conjunction with the embodiments and accompanied by the drawings.

[0013] Please refer to the appendix Figure 1 , a water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution and high solid content, by weight, includes 10 to 30 parts of polymer A and 70 to 90 parts of polymer B; The polymer A is an acrylic emulsion with a single-peak distribution at 100 to 200 nm and a ketone carbonyl group on the surface, and the polymer B is an acrylic emulsion with a double-peak distribution at 40 to 80 nm and 300 to 800 nm and a hydrazide group on the surface.

[0014] As can be seen from the above description, the beneficial effects of the present invention are as follows: The three-peak distribution high-solid-content aqueous acrylic pressure-sensitive adhesive emulsion of the present invention mixes the single-peak distribution polymer A and the double-peak distribution polymer B. The latex particles of polymer A can further fill the gaps between the latex particles of polymer B, thereby achieving a high solid content (≥62%) and a low viscosity (≤800 mPa·s). Moreover, the pressure-sensitive adhesive emulsion of the present invention has a lower viscosity than the individual polymer A or polymer B emulsions. Among them, polymer A can enhance the initial tack of the pressure-sensitive adhesive emulsion. The components of polymer A and polymer B are similar, and their compatibility is excellent. They are easy to add and are very stable even after long-term storage after mixing. During the film-forming process and later stage of the pressure-sensitive adhesive, the ketone carbonyl group on the surface of polymer A and the hydrazide group on the surface of polymer B can promote the chemical fusion between the two latex particles and greatly reduce the gap between the particles through the "hydrazide crosslinking" reaction, thereby improving water resistance and other properties.

[0015] Furthermore, polymer A has excellent monodisperse particle size, with its PDI (particle size aggregation index) ≤0.1, preferably PDI ≤0.08, and more preferably PDI ≤0.05.

[0016] Furthermore, the PDI of polymer B ≥0.1, preferably PDI ≥0.15, and more preferably PDI ≥0.20.

[0017] Furthermore, by weight, it also includes 0.1~0.5 parts of defoamer and 0.01~0.05 parts of bactericide.

[0018] Another technical solution adopted by the present invention is: A preparation method of the above-mentioned three-peak distribution high-solid-content aqueous acrylic pressure-sensitive adhesive emulsion, comprising the following steps: adding polymer B, stirring and dropping polymer A, adding defoamer and bactericide, mixing evenly and filtering to obtain the three-peak distribution high-solid-content aqueous acrylic pressure-sensitive adhesive emulsion.

[0019] Furthermore, it includes the following steps: adding polymer B, controlling the stirring speed at 100~500 r / m, dropping polymer A into the kettle evenly within 10~60 min under stirring, keeping the speed unchanged and continuing to stir for 30~60 min, then adding defoamer and bactericide, and filtering to obtain the three-peak distribution high-solid-content aqueous acrylic pressure-sensitive adhesive emulsion.

[0020] As can be seen from the above description, polymer A and polymer B are uniformly dispersed in water in the form of emulsion.

[0021] Furthermore, the preparation method of polymer A includes the following steps: S1: Mix a part of emulsifier with deionized water to form a mixed solution, mix the hard monomer, soft monomer, carboxyl-containing unsaturated monomer and chain transfer agent evenly and drop them into the mixed solution to form a pre-emulsion A; S2: Add the remaining emulsifier and deionized water to the reaction kettle and stir evenly. Then add part of the pre-emulsion A and part of the initiator to form a seed emulsion. S3: Drop the remaining pre-emulsion A and the remaining initiator into the seed emulsion. During the dropping process, add a crosslinkable unsaturated monomer containing a ketone carbonyl group. After the dropping is completed, carry out the reaction, and then filter to obtain Polymer A.

[0022] Furthermore, the preparation method of Polymer A includes the following steps: S1: Mix part of the emulsifier and deionized water, stir at a speed of 500 - 1000 rpm for 10 - 30 min to form a mixed solution. Mix the hard monomer, soft monomer, carboxyl-containing unsaturated monomer, and chain transfer agent evenly and drop them into the mixed solution within 15 - 45 min to form pre-emulsion A. S2: Add the remaining emulsifier and deionized water to the reaction kettle and stir evenly. Heat up to 70 - 90 °C, add 3 - 10 wt% of pre-emulsion A and an aqueous solution of part of the initiator, and keep warm for 15 - 30 min to form a seed emulsion. S3: Drop the remaining pre-emulsion A and the aqueous solution of the remaining initiator into the seed emulsion at a uniform speed, control the temperature at 70 - 90 °C, and the dropping process lasts for 120 - 240 min. When there is still 1 / 4 - 1 / 10 of the dropping time left, add an aqueous solution of the crosslinkable unsaturated monomer containing a ketone carbonyl group to pre-emulsion A, stir for 1 - 5 min, and then continue to drop. After the dropping is completed, continue the reaction for 60 - 180 min, and then filter to obtain Polymer A.

[0023] As can be seen from the above description, the Polymer A prepared by the present invention is an acrylic emulsion with a relatively high theoretical glass transition temperature and a relatively low molecular weight, -5 °C ≤ Tg ≤ 30 °C, Mw = 2000 - 20000 Daltons, which can enhance the initial tack of the pressure-sensitive adhesive emulsion.

[0024] Furthermore, when naming the monomers or compounds of the present invention, the prefix "(meth)acrylo" should include "acrylo" and "methacrylo", and the prefix "(n, iso)alkyl ester" should include "n-alkyl ester" and "iso-alkyl ester".

[0025] Furthermore, based on the weight of the solid content in Polymer A being 100%: The content of the hard monomer is 40% - 50%, the content of the soft monomer is 40% - 50%, the content of the crosslinkable unsaturated monomer containing a ketone carbonyl group is 0.1% - 2%, the content of the carboxyl-containing unsaturated monomer is 0.5% - 1.5%, the content of the chain transfer agent is 3% - 10%, the content of the emulsifier (calculated according to the effective solid content of the emulsifier) is 0.5% - 3%, and the content of the initiator is 0.15 - 0.75%.

[0026] Furthermore, the hard monomer comprises at least one (meth)acrylic acid alkyl ester or aromatic vinyl unsaturated compound, and the Tg of the homopolymer of the hard monomer is ≥ 20°C.

[0027] Furthermore, the hard monomer is a composition of one or two of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and styrene. Preferably, the hard monomer is methyl methacrylate.

[0028] Furthermore, the soft monomer comprises at least one (meth)acrylic acid alkyl ester, and the Tg (glass transition temperature) of the homopolymer of the soft monomer is ≤ -20°C.

[0029] Furthermore, the soft monomer is a composition of one or two of (n-, iso-)butyl acrylate, amyl acrylate, (meth)acrylic acid n-hexyl ester, (meth)acrylic acid heptyl ester, (meth)acrylic acid (n-, iso-)octyl ester, (meth)acrylic acid isodecyl ester, (meth)acrylic acid dodecyl ester and (meth)acrylic acid octadecyl ester. Preferably, the soft monomer is butyl acrylate or isooctyl acrylate, or a composition of both.

[0030] Furthermore, the crosslinkable unsaturated monomer containing a ketone carbonyl group is one of diacetone acrylamide and (meth)acrylic acid acetoacetoxyethyl ester.

[0031] Furthermore, the crosslinkable unsaturated monomer containing a ketone carbonyl group is added together with other monomers or added alone. When adding, it is added once or multiple times at any time period during polymerization. Preferably, it is added in the later stage of polymerization, and the addition time is 50 - 99% of the progress of monomer dropping completion, preferably 70 - 95%, more preferably 80 - 90%.

[0032] From the above description, it can be seen that the crosslinkable unsaturated monomer containing a ketone carbonyl group is added in the later stage of polymerization, and it is more likely to graft on the outer shell of polymer A.

[0033] Furthermore, the carboxyl-containing unsaturated monomer is selected from one of acrylic acid and methacrylic acid, and preferably methacrylic acid.

[0034] Furthermore, the chain transfer agent is a sulfur-containing organic compound with a molecular weight ≤ 1000 g / mol, and can be selected from one of mercaptoethanol, mercaptopropionic acid, n-dodecyl mercaptan, tert-dodecyl mercaptan, isooctyl mercaptopropionate and isooctyl mercaptoacetate. Preferably, it is n-dodecyl mercaptan. The chain transfer agent is added to the bottom liquid of the kettle (seed emulsion) or continuously dropped after being mixed evenly with the monomer. Preferably, it is continuously dropped after being mixed evenly with the monomer.

[0035] Further, the emulsifier is at least one of anionic, cationic and non-ionic surfactants, and the molecular weight of the emulsifier is less than 2000 g / mol; preferably an anionic-nonionic composite emulsifier, a compound with the general formula R(CH2CH2O)mXSO4, where R is a fatty alcohol with C8-C20, m = 2-35, X is an alkali metal or ammonium, and commercial products such as Disponil FES32, Disponil FES77, Disponil BES20 and ABEX 8018R.

[0036] Further, the emulsifier is a polymerizable emulsifier containing unsaturated bonds, and is selected from at least one of ADEKA SR-10, Dai-ichi Kogyo Seiyaku Hitenol BC-10 and Solvay Reactsurf ® 2490.

[0037] Further, the emulsifier is added to the bottom liquid of the kettle (seed emulsion) and the pre-emulsion. As one scheme, the proportion of the emulsifier in the pre-emulsion is much larger than that in the bottom liquid of the kettle, and the ratio is (5-10):1. As another scheme, no emulsifier is added to the bottom liquid of the kettle.

[0038] As can be seen from the above description, the emulsifier is a polymerizable emulsifier containing unsaturated bonds, which can improve the water whitening resistance.

[0039] Further, the initiator is one of potassium persulfate, sodium persulfate and ammonium persulfate.

[0040] Further, the initiator is added once, or added multiple times, or added continuously. Preferably, part of the initiator is added when polymerizing the seeds, and the proportion accounts for 5-50% of the total initiator, and the preferred proportion is 10-40%. The remaining initiator is continuously added dropwise simultaneously with the pre-emulsion, and the dropping time ends simultaneously with the pre-emulsion or slightly later than the monomer ending time.

[0041] Further, Polymer A has a solid content of 50-65% and a viscosity of 100-10000 mpa·s, and preferably a viscosity of 500-5000 mpa·s.

[0042] Further, the preparation method of Polymer B includes the following steps: S1: Mix the emulsifier with deionized water to form a mixed solution, and mix the hard monomer, soft monomer, carboxyl-containing unsaturated monomer and ureido-containing ethylenically unsaturated monomer evenly and drop them into the mixed solution to form a pre-emulsion B; S2: Mix deionized water and part of the crystal seeds, and add part of the initiator to obtain a mixed solution B; S3: The pre-emulsion B, the remaining initiator and the ammonia dilution are separately added dropwise to the mixed solution B at the same time, and the remaining crystal seeds and the cross-linkable unsaturated monomer containing a hydrazide group are added during the addition process; after the addition is completed, the reaction is carried out, and the residual monomer is treated by redox reaction to obtain polymer B.

[0043] Furthermore, the preparation method of polymer B comprises the following steps: S1: Mix the emulsifier with deionized water and stir at a speed of 500-1000 rpm for 10-30 minutes to form a mixed solution. Evenly mix the hard monomer, soft monomer, carboxyl group-containing unsaturated monomer and urea group-containing ethylenically unsaturated monomer and dropwise add the mixed solution within 15-45 minutes. Continue stirring for 30-60 minutes to form a pre-emulsion B. S2: Mix deionized water and some crystal seeds, raise the temperature to 70-90°C, add some initiator, and obtain mixed solution B; S3: The pre-emulsion B, the remaining initiator aqueous solution and the ammonia dilution solution are separately added dropwise to the mixed solution B at the same time, and the temperature is maintained at 75~90°C. The addition process lasts for 180~300 minutes. When 1 / 4~1 / 10 of the addition time is left, the remaining crystal seeds are added at one time, and a 10% aqueous dispersion of a cross-linkable unsaturated monomer containing a hydrazide group is added to the pre-emulsion B, stirred for 0.5~1.5 minutes, and then continued to add dropwise; after the addition is completed, the heat is continued for 30~120 minutes, and the residual monomers are treated by redox reaction, and the temperature is lowered to 40~50°C to obtain polymer B.

[0044] From the above description, it can be seen that the polymer B of the present invention constructs a bimodal structure through the method of secondary seed uptake. Compared with the traditional seed preparation method, the present invention adopts a microemulsion method to prepare seeds, which has the advantages of low residual rate, high stability and strong repeatability. At the same time, it adopts a special synthesis process, has an extremely low emulsifier ratio, and improves the water whitening resistance of the pressure-sensitive adhesive latex.

[0045] Furthermore, the second crystal seed addition is preferably performed when at least 70% of the monomers, more preferably 80% of the monomers, and most preferably 90% of the monomers have been added to the reactor. The addition method is either a one-time rapid addition or continuous dropwise addition, preferably a one-time rapid addition.

[0046] Furthermore, based on the weight of the solid content in polymer B being 100%, The content of the hard monomer is 5% - 16.55%, the content of the soft monomer is 75% - 92%, the content of the crosslinkable unsaturated monomer containing a hydrazide group is 0.1% - 1%, the content of the carboxyl-containing unsaturated monomer is 1% - 3%, the content of the ethylenically unsaturated monomer containing a urea group is 1% - 3%, the content of the crystal seeds (calculated based on the effective solid content of the crystal seeds) is 0.1% - 0.5%, the content of the emulsifier (calculated based on the effective solid content of the emulsifier) is 0.05% - 0.2%, and the content of the initiator is 0.15 - 0.75%.

[0047] Furthermore, the hard monomer includes at least one hard monomer of (meth)acrylic acid alkyl ester or aromatic vinyl unsaturated compound, and the Tg of its homopolymer is ≥ 20°C.

[0048] Furthermore, the hard monomer is one or a combination of two of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and styrene.

[0049] Furthermore, the hard monomers in polymer A and polymer B are the same or different. Preferably, the hard monomers in polymer A and polymer B are the same.

[0050] Furthermore, the soft monomer includes at least one soft monomer of (meth)acrylic acid alkyl ester, and the Tg of its homopolymer is ≤ -20°C.

[0051] Furthermore, the soft monomer is one or a combination of two of (n-, i-)butyl acrylate, amyl acrylate, (n-, i-)hexyl (meth)acrylate, heptyl (meth)acrylate, (n-, i-)octyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate.

[0052] Furthermore, the soft monomers in polymer A and polymer B are the same or different. Preferably, the soft monomers in polymer A and polymer B are the same.

[0053] Furthermore, the crosslinkable unsaturated monomer containing a hydrazide group is one of dihydrazide maleate, dihydrazide fumarate, and dihydrazide itaconate. Dihydrazide maleate, dihydrazide fumarate, and dihydrazide itaconate are all self-made products. Taking dihydrazide maleate as an example, its preparation method is briefly described as follows: Using a one-step method, dihydrazide maleate is obtained by refluxing dialkyl maleate and hydrazine hydrate for an appropriate time under heating conditions, then cooling and crystallizing, and finally obtaining solid dihydrazide maleate through filtration, washing, drying, and recrystallization.

[0054] Furthermore, the crosslinkable unsaturated monomer containing a hydrazide group is added together with other monomers or added separately. It is added once or multiple times at any time during the polymerization. Preferably, it is added in the later stage of the polymerization, and the addition time is 50% - 99% of the completion progress of the monomer dropping, preferably 70 - 95%, more preferably 80 - 90%.

[0055] As can be seen from the above description, the crosslinkable unsaturated monomer containing hydrazide group is added in the later stage of polymerization, and can be grafted more preferentially on the outer shell of polymer B.

[0056] Furthermore, the unsaturated monomer containing carboxyl group is one of acrylic acid and methacrylic acid.

[0057] Furthermore, the unsaturated monomers containing carboxyl group in polymer A and polymer B are the same or different. Preferably, the unsaturated monomers containing carboxyl group in polymer A and polymer B are the same, both being methacrylic acid.

[0058] Furthermore, the ethylenically unsaturated monomer containing ureido group is ethoxyethyl acryloyl ethyl urethane and / or acrylamide ethyl urethane ethoxy ester. Preferably, it is one of BASF UMA25, Solvay SIPOMER WAM Ⅱ and Nanjing Kaishitong Ecusollent®WAM Ⅲ.

[0059] As can be seen from the above description, the ethylenically unsaturated monomer containing ureido group has a low glass transition temperature, but has a strong polar group ureido, which can improve the cohesion without bringing negative effects of decreasing initial adhesion.

[0060] Furthermore, the crystal seeds are polystyrene or polymethyl methacrylate latex particles prepared by the microemulsion method, and the diameter of the crystal seeds is 30 - 50 nm.

[0061] Furthermore, the preparation method of the crystal seeds includes the following steps: mixing the emulsifier and water evenly to form the bottom liquid of the kettle, adding the initiator aqueous solution at one time, and uniformly dropping the mixture of styrene or methyl methacrylate and n-pentanol, polymerizing until the residual monomer rate is less than 0.5%, and filtering and collecting to obtain crystal seeds with a particle size of 30 - 50 nm.

[0062] As can be seen from the above description, compared with the preparation of seeds in traditional emulsions, the crystal seeds of the present invention have the advantages of excellent monodispersity, good stability and good reproducibility. Based on these crystal seeds, emulsion polymerization is carried out, ensuring the stability and reproducibility of polymer B emulsion.

[0063] Furthermore, in the preparation method of the crystal seeds, the emulsifier is selected from one of sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the emulsifier accounts for 5 - 20 wt%, preferably 10 - 15 wt% of the monomer mass in the crystal seeds; the initiator is selected from one of potassium persulfate, sodium persulfate and ammonium persulfate, and the emulsifier accounts for 0.1 - 1 wt%, preferably 0.3 - 0.8 wt% of the monomer mass in the crystal seeds. n-Pentanol accounts for 0.1 - 10 wt%, preferably 1 - 5 wt% of the monomer mass in the crystal seeds.

[0064] Further, the PDI of the crystal seeds is ≤0.2, more preferably PDI ≤0.15.

[0065] Further, the emulsifier is at least one of anionic, cationic and non-ionic surface active substances, and the molecular weight of the emulsifier is less than 2000 g / mol; preferably a combination of anionic and non-ionic emulsifiers, a compound with the general formula R(CH2CH2O)mXSO4, where R is a fatty alcohol with C8-C20, m = 2-35, X is an alkali metal or ammonium, and commercial products such as Disponil FES32, Disponil FES77, Disponil BES20 and ABEX 8018R.

[0066] Further, the emulsifier is a polymerizable emulsifier containing unsaturated bonds, selected from at least one of ADEKA SR-10, Dai-ichi Kogyo Seiyaku Hitenol BC-10 and Solvay Reactsurf® 2490.

[0067] As can be seen from the above description, the emulsifier is a polymerizable emulsifier containing unsaturated bonds, which can improve the water whitening resistance.

[0068] Further, the emulsifiers of polymer A and polymer B are the same or different, preferably the same.

[0069] Further, the addition amount of the emulsifier is less than 0.2% of the total solids, more preferably less than 0.1%, and all are added to the pre-emulsion.

[0070] Further, the initiator is one of potassium persulfate, sodium persulfate and ammonium persulfate.

[0071] Further, the initiator is added once or multiple times, or preferably added once to the bottom liquid of the kettle, and the addition time is earlier than the monomer addition time.

[0072] Further, the initiators of polymer A and polymer B are the same or different, preferably the same, both being ammonium persulfate.

[0073] Further, polymer B has a solid content of 63-70% and a viscosity of 500-10000 mpa·s, preferably a viscosity of 1000-8000 mpa·s.

[0074] The abbreviations, partial raw materials and basic parameters of some reagents in the following examples are as follows: ABS-23: Sodium dodecylbenzenesulfonate, 23% effective solid content, Shanghai Zhongcheng Fine Chemicals; SR-10: Reactive anionic emulsifier, ADEKA Corporation; Disponil FES77: Sodium C12-C14 alcohol ether sulfate (30EO), 33% active solids content, BASF; Ecusollent® WAM Ⅲ: Ethylene urea methacrylate ethoxylate, 50% active content, solvent is water, Nanjing Kaishitong New Materials Co., Ltd.; The defoamer is Coadd DF-1383 from Puwei New Materials Co., Ltd., and the component is mineral oil-based defoamer; The bactericide is Emarcure™ 4225 from Yimo Biotechnology Co., Ltd., and the component is a mixture of isothiazolinones; MAA: Methacrylic acid; St: Styrene; MMA: Methyl methacrylate; NDM: n-Dodecyl mercaptan; BA: n-Butyl acrylate; 2-EHA: Isooctyl acrylate; DAAM: Diacetone acrylamide; AAEM: Acetylacetoxyethyl methacrylate; APS: Ammonium persulfate, initiator; MDH: Maleic dihydrazide, self-made, method as follows: Drop a mixture of 1 mol of diethyl maleate and 0.2 g of p-methoxy phenol into a mixture of 4 mol of 85% hydrazine hydrate and 250 ml of absolute ethanol within 90 min, control the dropping temperature at about 60 °C, after dropping, raise the temperature to 70 °C and react for 4 hours, then cool to 5 °C for crystallization, and then obtain solid maleic dihydrazide after multiple filtration, washing, drying and recrystallization.

[0075] IDH: Itaconic dihydrazide, self-made, method as follows: Drop a mixture of 1 mol of diethyl itaconate and 0.2 g of p-methoxy phenol into a mixture of 4 mol of 85% hydrazine hydrate and 250 ml of absolute ethanol within 90 min, control the dropping temperature at about 60 °C, after dropping, raise the temperature to 70 °C and react for 4 hours, then cool to 5 °C for crystallization, and then obtain solid itaconic dihydrazide after multiple filtration, washing, drying and recrystallization.

[0076] Preparation of crystal seeds: Add 32.87 g of ABS-23 and 158.14 g of deionized water to the reaction kettle, stir to dissolve and heat up to 85 °C, add 6.86 g of 7% ammonium persulfate aqueous solution at one time, and uniformly drop a mixture of 75.78 g of St and 1 g of n-pentanol within the next 3 hours. Keep the polymerization at 85 °C until the residual monomer rate in the kettle is less than 0.1%, and filter to collect the product. After testing, the solid content of the crystal seeds is 32.9%, the Z-average particle size is 31.22 nm, and PDI = 0.14.

[0077] Particle size test in the following examples: Measure the Z-average particle size of a 0.4% by weight polymer emulsion dilution at room temperature of 25 °C using a BeNano90 Zeta from Baxter Instruments.

[0078] Viscosity test in the following examples: Use a Fangrui instrument rotational viscometer to test the viscosity value at a shear rate of 60 r / m at room temperature of 25°C.

[0079] Example 1 of the present invention is: Preparation of Polymer AⅠ S1: As shown in Table 1, mix 87.5% of Component A6 with deionized water, stir at a rotation speed of 700 rpm for 15 min to form a mixed solution. Mix Components A1, A2, A4, and A5 evenly and drop them into the above mixed solution within 30 min, and continue stirring for 45 min to form pre-emulsion A; S2: Add 12.5% of Component A6 and deionized water to the reaction kettle and stir evenly. Heat up to 82°C, add 5% of pre-emulsion A at one time, add an aqueous solution of 33.33% Component A7, and keep warm for 20 min to form a seed emulsion; S3: Add the remaining pre-emulsion and an aqueous solution of 66.67% Component A7 to the reaction kettle at a constant speed, control the temperature at 82°C, and the dropping process lasts for 180 min. When there is still 1 / 6 of the dropping time left, add a 25% aqueous solution of Component A3 to the pre-emulsion, stir for 2 min, and then continue dropping; S4: After the dropping is completed, continue the reaction for 90 min, filter and collect to obtain Polymer AⅠ; Example 2 of the present invention is: Preparation of Polymer AⅡ S1: As shown in Table 1, mix all of Component A6 with deionized water, stir at a rotation speed of 700 rpm for 15 min to form a mixed solution. Mix Components A1, A2, A4, and A5 evenly and drop them into the above mixed solution within 30 min, and continue stirring for 45 min to form pre-emulsion A; S2: Add deionized water to the reaction kettle and stir evenly. Heat up to 82°C, add 7.5% of pre-emulsion A at one time, add an aqueous solution of 33.33% Component A7, and keep warm for 20 min to form a seed emulsion; S3: Add the remaining pre-emulsion and an aqueous solution of 66.67% Component A7 to the reaction kettle at a constant speed, control the temperature at 82°C, and the dropping process lasts for 180 min. When there is still 1 / 6 of the dropping time left, add a 25% aqueous solution of Component A3 to the pre-emulsion, stir for 2 min, and then continue dropping; S4: After the dropping is completed, continue the reaction for 90 min, filter and collect to obtain Polymer AⅡ.

[0080] Table 1

[0081] Example 3 of the present invention is: Preparation of Polymer BⅠ S1: As shown in Table 2, mix Component B7 with deionized water, stir at a speed of 700 rpm for 20 min to form a mixed solution, mix Component B1, Component B2, Component B4 and Component B5 uniformly and drop them into the above mixed solution within 25 min, and continue to stir for 30 min to form pre-emulsion B; S2: Add deionized water and part of Component B6 to the reaction kettle, heat up to 82 °C and add 20% aqueous solution of Component B8; S3: Add pre-emulsion B, 80% aqueous solution of Component B8 and ammonia water dilution to the reaction kettle simultaneously and uniformly through three channels, keep the temperature at 82 °C, the dropping process lasts for 200 min, and add the remaining Component B6 to the reaction kettle at one time when 1 / 8 of the dropping time remains. On the other hand, add 10% aqueous dispersion of Component B3 to pre-emulsion B and stir for 1 min before continuing to drop when 1 / 5 of the dropping time remains; S4: After the dropping is completed, keep the temperature for 60 min, and perform residual monomer treatment with redox reaction, cool down to 45 °C to obtain Polymer BⅠ; Example 4 of the present invention is: Preparation of Polymer BⅡ Example 4 is prepared by the same process as Example 3, the addition amounts of each component are as shown in Table 2, and the addition time of the second crystal seed is quickly added to the reaction kettle when 1 / 4 of the dropping time remains.

[0082] Example 5 of the present invention is: Preparation of Polymer BⅢ Example 5 is prepared by the same process as Example 3, the addition amounts of each component are as shown in Table 2, and the addition time of the second crystal seed is quickly added to the reaction kettle when 1 / 4 of the dropping time remains.

[0083] Example 6 of the present invention is: Preparation of Polymer BⅣ Example 6 is prepared by the same process as Example 3, the addition amounts of each component are as shown in Table 2, and the addition time of the second crystal seed is the same as that in Example 3.

[0084] Comparative Example 1 of the present invention is: Preparation of Polymer BⅤ (not of the present invention) Comparative Example 1 is prepared by the same process as Example 3, the addition amounts of each component are as shown in Table 2, and only one crystal seed is added.

[0085] Table 2

[0086] Note: The components of the above Polymer B are counted by non-volatile matter.

[0087] Example 7 of the present invention is: Preparation of high-solid water-based pressure-sensitive adhesive emulsion samples 1 to 6 As shown in Table 3, control the stirring speed at 300 r / m, and uniformly drop polymer emulsion A (AⅠ or AⅡ) into polymer B (BⅠ - BⅣ) within 30 min, continue stirring for 30 min, add a bactericide and an antifoaming agent, and then filter to obtain a waterborne pressure-sensitive adhesive emulsion sample with a three-peak distribution and high solid content.

[0088] Comparative Example 2 of the present invention is: Preparation of waterborne pressure-sensitive adhesive emulsion sample 7 As shown in Table 3, control the stirring speed at 300 r / m, and uniformly drop 20 parts of polymer AⅡ into 80 parts of polymer BⅤ (not of the present invention) within 30 min, continue stirring for 30 min, add a bactericide and an antifoaming agent, and then filter to obtain sample 7 with a bimodal distribution.

[0089] Comparative Example 3 of the present invention is: Preparation of waterborne pressure-sensitive adhesive emulsion sample 8 As shown in Table 3, without adding polymer A, only containing polymer BⅣ, add a bactericide and an antifoaming agent, and then filter to obtain sample 8 with a bimodal distribution.

[0090] Comparative Example 4 of the present invention is: Preparation of waterborne pressure-sensitive adhesive emulsion sample 9 As shown in Table 3, uniformly drop 35 parts of polymer AⅠ into 65 parts of polymer BⅣ within 30 min, continue stirring for 30 min, add a bactericide and an antifoaming agent, and then filter to obtain sample 9 with a three-peak distribution.

[0091] Table 3

[0092] Note: The viscosity of 62% solid content refers to the viscosity when samples 1 - 9 are all diluted with an appropriate amount of water to adjust the solid content to 62 ± 0.1%. The results in Table 3 show that the pressure-sensitive adhesive samples 1 - 6 prepared by the present invention all achieve high solid content (about 62%) and low viscosity (≤800 mPa·s). Taking sample 1 as an example, its particle size distribution diagram has an obvious three-peak structure as shown in the appendix. Figure 1 The peaks are peak 1 with a size of 48 nm, peak 2 with a size of 120 nm, and peak 3 with a size of 624 nm respectively. Mixing small and medium-sized latex particles in the gaps between large-sized latex particles can further improve the packing density of latex particles compared with the bimodal distribution, thereby further increasing the solid content and reducing the viscosity. Finally, the viscosity of the pressure-sensitive adhesive emulsion is lower than the viscosities of polymer A and polymer B respectively. In non-invention sample 7, polymer BV only has a single peak due to no multi-step seed addition, and has a bimodal structure after combining with polymer AⅡ, and its viscosity of 62% solid content is significantly higher than that of samples 1 - 6 of the present invention. In non-invention sample 8, only polymer B is contained without polymer A, and its final viscosity of 62% solid content is also significantly larger. In non-invention sample 9, the proportion of polymer A exceeds 30% of the total polymer, and the final viscosity is also relatively large.

[0093] The performance tests were carried out after adding 0.2 wt% of TEGO® Wet KL 245 wetting agent to the emulsions of Samples 1-9 respectively. The specific test methods are as follows, and the test results are shown in Table 4: Preparation of pressure-sensitive tape: The pressure-sensitive adhesive was evenly coated onto the corona-treated BOPP film using a 70-μm wet film applicator or wire bar, cut into strips of 25×200 mm, placed in an 80°C oven and dried for 5 min, taken out and cooled, and then the three-force test was carried out. Three samples were tested for each performance, and the results were averaged three times.

[0094] 1.1. Initial tack force test by rolling ball: The initial tack force was tested according to Test Method B (inclined trough rolling ball method) of GB / T 4852-2002 standard; 1.2. 180° peel force test: The 180° peel force of the test specimen after 24 h was tested according to GB / T 2792-2014 standard; 1.3. Holding tack force test: The holding tack force of the test specimen was tested according to GB / T4851-2014 standard.

[0095] 2. Water-white resistance behavior test: The pressure-sensitive adhesive was evenly coated onto a glass plate using a 70-μm wet film applicator or wire bar, then transferred to an 80°C oven and dried for 5 min, and naturally cooled and then immersed in water. Record the grade of the whitening of the adhesive film at 60 min, and the results are shown in Table 4.

[0096] Among them, the water-white resistance of the adhesive film is divided into five grades from 0 to 4, specifically as follows: 0: The adhesive film shows almost no bluing; 1: The adhesive film shows very slight bluing; 2: The adhesive film shows obvious bluing; 3: The adhesive film shows obvious bluish-white; 4: The adhesive film shows complete whitening Table 4

[0097] The results in Table 4 show that the pressure-sensitive adhesive samples 1-6 prepared by the present invention all have excellent three-force performance and good water-white resistance performance. The performance of Sample 7 is also close to that of the pressure-sensitive adhesive of the present invention, but the viscosity is too high and it needs to be diluted before sample preparation. Since Sample 8 does not add Polymer A acting as a tackifier, its initial tack performance significantly declines, and the later peel strength is also weak. At the same time, due to the absence of hydrazide crosslinking, the water-white resistance of the system is also poor. Sample 9 adds an excessive amount of Polymer A. Although its initial tack force exceeds the system of the present invention, its holding tack force declines a lot. Similarly, due to the excessive Polymer A not forming a sufficient crosslinking density, a large amount of low-molecular-weight Polymer A causes a significant decline in water-white resistance.

[0098] Example 8 of the present invention is: A preparation method of a three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion, and the steps are as follows: S1: Preparation of Polymer A: S11: As shown in Table 5, 87.5% of component A6 was mixed with deionized water and stirred at 500 rpm for 30 minutes to form a mixed solution. Components A1, A2, A4, and A5 were mixed evenly and added dropwise to the mixed solution within 30 minutes. Stirring was continued for 30 minutes to form a pre-emulsion A. S12: 12.5% of component A6 and deionized water were added to the reactor and stirred evenly. The temperature was raised to 70°C, and 3% of pre-emulsion A was added at once. 33.33% of the aqueous solution of component A7 was added and the mixture was kept warm for 30 minutes to form a seed emulsion. S13: The remaining pre-emulsion and 66.67% aqueous solution of component A7 were uniformly added to the reactor, the temperature was controlled at 70°C, and the addition process lasted for 240 minutes. When 1 / 4 of the addition time was left, 25% aqueous solution of component A3 was added to the pre-emulsion, stirred for 1 minute, and continued to be added dropwise; S14: After the addition is complete, the reaction is continued for 60 minutes, and polymer A is obtained by filtration and collection; S2: Preparation of polymer B: S21: Component B7 was mixed with deionized water and stirred at 500 rpm for 30 minutes to form a mixed solution. Components B1, B2, B4, and B5 were mixed uniformly and added dropwise to the mixed solution within 15 minutes. Stirring was continued for 40 minutes to form a pre-emulsion B. S22: Deionized water and a portion of component B6 are added to a reactor, the temperature is raised to 70°C, and a 20% aqueous solution of component B8 is added; S23: Pre-emulsion B, 80% aqueous solution of component B8, and diluted ammonia solution were added simultaneously and uniformly to the reactor through three channels, maintaining the temperature at 70°C. The addition process continued for 300 minutes. When 1 / 4 of the addition time remained, the remaining component B6 was added to the reactor all at once. Meanwhile, when 1 / 4 of the addition time remained, a 10% aqueous dispersion of component B3 was added to pre-emulsion B, stirred for 1 minute, and then continued to be added dropwise. S24: After the addition is complete, the temperature is maintained for 30 minutes, and the residual monomer is treated by redox reaction, and the temperature is lowered to 40° C. to obtain polymer B; S3: Control the stirring speed to 100 r / m, add polymer emulsion A to polymer B at a uniform speed within 10 minutes, continue stirring for 60 minutes, add bactericide and defoamer, and filter to obtain a trimodal distribution high solid content aqueous pressure-sensitive adhesive latex sample, named Sample 10.

[0099] Table 5

[0100] Example 9 of the present invention is: a method for preparing a trimodal distribution high solid content aqueous acrylic pressure-sensitive adhesive emulsion, the steps are as follows: S1: Preparation of Polymer A: S11: As shown in Table 5, 87.5% of Component A6 is mixed with deionized water, stirred at a speed of 1000 rpm for 10 min to form a mixed solution. Component A1, Component A2, Component A4, and Component A5 are mixed evenly and dropped into the above mixed solution within 30 min, and then stirred continuously for 15 min to form pre-emulsion A; S12: 12.5% of Component A6 and deionized water are added to the reaction kettle and stirred evenly, heated to 90 °C, 10% of pre-emulsion A is added at one time, and an aqueous solution of 33.33% Component A7 is added, and kept warm for 15 min to form a seed emulsion; S13: The remaining pre-emulsion and an aqueous solution of 66.67% Component A7 are added to the reaction kettle at a constant speed, the temperature is controlled at 90 °C, the dropping process lasts for 120 min, and when there is still 1 / 10 of the dropping time left, a 25% aqueous solution of Component A3 is added to the pre-emulsion, stirred for 5 min, and then the dropping continues; S14: After the dropping is completed, continue to react for 180 min, filter and collect to obtain Polymer A; S2: Preparation of Polymer B: S21: Component B7 is mixed with deionized water, stirred at a speed of 1000 rpm for 10 min to form a mixed solution. Component B1, Component B2, Component B4, and Component B5 are mixed evenly and dropped into the above mixed solution within 45 min, and then stirred continuously for 60 min to form pre-emulsion B; S22: Deionized water and a part of Component B6 are added to the reaction kettle, heated to 90 °C, and a 20% aqueous solution of Component B8 is added; S23: Pre-emulsion B, an 80% aqueous solution of Component B8, and an ammonia water dilution solution are added to the reaction kettle simultaneously and at a constant speed through three channels, keeping the temperature at 90 °C, the dropping process lasts for 180 min, and when there is still 1 / 10 of the dropping time left, the remaining Component B6 is added to the reaction kettle at one time. On the other hand, when there is still 1 / 10 of the dropping time left, a 10% aqueous dispersion of Component B3 is added to pre-emulsion B, stirred for 1 min, and then the dropping continues; S24: After the dropping is completed, continue to keep warm for 120 min, and carry out residual monomer treatment with redox reaction, cool down to 50 °C to obtain Polymer B; S3: Control the stirring speed at 500 r / m, drop Polymer Emulsion A into Polymer B at a constant speed within 60 min, continue to stir for 40 min, add a bactericide and an antifoaming agent, and filter to obtain a three-peak distribution high solid content water-based pressure-sensitive adhesive emulsion sample, named Sample 11.

[0101] Example 10 of the present invention is: a high solid content water-based acrylic pressure-sensitive adhesive emulsion prepared by the preparation method of Example 9.

[0102] In summary, the three-peak distribution high-solid waterborne acrylic pressure-sensitive adhesive emulsion and its preparation method provided by the present invention have the following advantages: 1. The high-solid waterborne acrylic pressure-sensitive adhesive emulsion of the present invention constructs a stable three-peak particle size distribution through the combination of polymer A and polymer B. The small and medium-sized latex particles are fully filled in the gaps between the large-sized latex particles, further improving the packing density of the latex particles. The viscosity of the obtained high-solid waterborne acrylic pressure-sensitive adhesive emulsion is lower than that of the emulsion of polymer A or polymer B alone, thereby achieving high solid content (≥62%) and low viscosity (≤800 mPa·s).

[0103] 2. The seed used in polymer B of the present invention is a seed prepared by the microemulsion method, which has the advantages of good monodispersity, high stability and strong repeatability compared with the traditional emulsion seed preparation method. Through the process of adding the seed twice, the prepared polymer B is a high-solid emulsion with a bimodal distribution, with a low gel rate of the product and excellent repeatability. At the same time, polymer B uses a special synthesis process to maintain a low gel rate and stability of the emulsion under the condition of low emulsifier addition amount (≤2‰), which significantly improves the water whitening resistance of the emulsion.

[0104] 3. Polymer A of the present invention is an acrylic emulsion with a relatively high theoretical glass transition temperature and a relatively low molecular weight, -5°C ≤ Tg ≤ 30°C, Mw = 2000 - 20000 daltons, which can act as a "tackifying resin" to improve the initial tack of the pressure-sensitive adhesive. Compared with traditional "tackifying resins" such as waterborne rosin resin and terpene resin, polymer A can greatly improve the compatibility and yellowing resistance of the pressure-sensitive adhesive; polymer A is close to polymer B in composition, and the two have excellent compatibility, are easy to add and are very stable during long-term storage.

[0105] 4. The pressure-sensitive adhesive emulsion of the present invention grafts a ketone carbonyl group and a hydrazide group on the surfaces of polymer A and polymer B respectively. During the film-forming process, the gap between the latex particles can be reduced through the "ketone-hydrazide crosslinking" reaction, improving the denseness of the adhesive film, which greatly improves the water whitening resistance and cohesion of the adhesive film.

[0106] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in the related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution and high solid content, characterized in that By weight, it includes 10 to 30 parts of polymer A and 70 to 90 parts of polymer B; The polymer A is an acrylic emulsion having a single-peak distribution at 100 to 200 nm and containing a ketone carbonyl group on the surface, and the polymer B is an acrylic emulsion having a bimodal distribution at 40 to 80 nm and 300 to 800 nm and containing a hydrazide group on the surface.

2. The high-solid water-based acrylic pressure-sensitive adhesive emulsion with a three-peak distribution according to claim 1, wherein By weight, it further includes 0.1 to 0.5 parts of an antifoaming agent and 0.01 to 0.05 parts of a bactericide.

3. A method for preparing a three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion as described in claim 1 or 2, characterized in that, It includes the following steps: Add polymer B, stir and dropwise add polymer A, add the antifoaming agent and the bactericide, mix evenly and filter to obtain a three-peak distribution high-solid content water-based acrylic pressure-sensitive adhesive emulsion.

4. The preparation method of the three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion according to claim 3, characterized in that The preparation method of the polymer A includes the following steps: S1: Mix part of the emulsifier with deionized water to form a mixed solution, mix the hard monomer, soft monomer, carboxyl-containing unsaturated monomer and chain transfer agent evenly and drop them into the mixed solution to form a pre-emulsion A; S2: Add the remaining emulsifier and deionized water to the reaction kettle and stir evenly, add part of the pre-emulsion A and part of the initiator to form a seed emulsion; S3: Drop the remaining pre-emulsion A and the remaining initiator into the seed emulsion, and add a crosslinkable unsaturated monomer containing a ketone carbonyl group during the dropping process; after the dropping is completed, carry out the reaction, and then filter to obtain polymer A.

5. The preparation method of the three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion according to claim 4, characterized in that, The hard monomer contains at least one (meth)acrylic acid alkyl ester or aromatic vinyl unsaturated compound, and the Tg of its homopolymer is ≥20 °C.

6. The preparation method of the three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion according to claim 4, characterized in that The soft monomer contains at least one (meth)acrylic acid alkyl ester, and the Tg of its homopolymer is ≤ -20 °C.

7. The preparation method of the three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion according to claim 3, wherein, The preparation method of the polymer B includes the following steps: S1: Mix the emulsifier with deionized water to form a mixed solution, mix the hard monomer, soft monomer, carboxyl-containing unsaturated monomer and urea-containing ethylenically unsaturated monomer evenly and drop them into the mixed solution to form a pre-emulsion B; S2: Mix deionized water and part of the crystal seeds, add part of the initiator to obtain a mixed solution B; S3: Drop the pre-emulsion B, the remaining initiator and the ammonia water dilution solution separately into the mixed solution B at the same time, and add the remaining crystal seeds and a crosslinkable unsaturated monomer containing a hydrazide group during the dropping process; after the dropping is completed, carry out the reaction, and carry out residual monomer treatment by redox reaction to obtain polymer B.

8. The preparation method of the three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion according to claim 7, characterized in that, The hard monomer contains at least one (meth)acrylic acid alkyl ester or aromatic vinyl unsaturated monomer, and the Tg of its homopolymer is ≥20 °C.

9. The preparation method of the three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion according to claim 7, characterized in that, The soft monomer contains at least (meth)acrylic acid alkyl ester, and the Tg of its homopolymer is ≤ -20 °C.

10. The preparation method of the three-peak distribution high-solid water-based acrylic pressure-sensitive adhesive emulsion according to claim 7, characterized in that, The crystal seeds are polystyrene or polymethyl methacrylate latex particles prepared by the microemulsion method, and the diameter of the crystal seeds is 30 to 50 nm.

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