An aqueous adhesion promoter for PP decorative film and its preparation method

Abstract

The present invention discloses an aqueous adhesion promoter for PP decorative films and its preparation method. A P[(C12-C18)-co-I]-b-PAA polymer is designed and prepared as an adhesion resin, and then further formulated into an adhesion promoter. This promoter does not require pre-treatment such as corona, flame, plasma, etc. on the PP decorative film. After being directly printed on the PP decorative film by gravure printing, it can greatly improve the printing leveling property, adhesion and water resistance of subsequent gravure water-based ink.

Description

Technical Field

[0001] The invention relates to a water-based adhesion promoter and a preparation method thereof, and in particular to a PP decorative film water-based adhesion promoter and a preparation method thereof. Background Art

[0002] PP decorative film is a kind of decorative film for paint-free furniture surface made of polypropylene. Its visual effect is comparable to that of wood veneer. It is very suitable for flat pasting, coating and conditional 3D blistering. PP decorative film has the advantages of scratch resistance, stain resistance, drug resistance and weather resistance. It is very suitable for the application of paint-free doors, cabinets and wall panels. Good resistance makes the decorative surface look new for a long time. In the face of various pollution, chemical agents and direct light conditions, it will never change color and the quality is consistent. This is something that many PVC films cannot achieve. In addition, PP decorative film does not contain 13 substances such as formaldehyde / acetaldehyde / toluene / xylene, heavy metals such as chromium / cadmium / lead / arsenic, no plasticizer is used in production, it can be degraded when recycled, and only releases water and carbon dioxide when burned, without producing any toxic gases, so it has become the preferred decorative material for homes, schools, hotels and other places. PP decorative film is very popular in the field of Japanese home furnishings, but it is still a niche product in China and is only used on a small scale in some high-end fields.

[0003] The main bottleneck limiting the application of PP decorative film lies in the wetting, leveling and adhesion of ink. Due to the low surface energy of PP decorative film, it is difficult for ordinary ink to achieve good adhesion on this substrate. To solve this drawback, it is usually necessary to pre-treat the PP decorative film with corona, flame, plasma, etc., or pre-coat a layer of chlorinated polypropylene primer (adhesion promoter). At present, chlorinated polypropylene is mainly an oily resin system. In recent years, Toyobo Co., Ltd. of Japan has developed some water-based chlorinated polypropylene products, but their effect on improving the adhesion of inks, especially water-based inks, is limited, and they are expensive, making it difficult to promote and apply them on a large scale in the field of PP decorative films. Summary of the invention

[0004] The purpose of the present invention is to provide a water-based adhesion promoter for PP decorative film and a preparation method thereof. The promoter does not require corona, flame, plasma or other pretreatment of the PP decorative film. After being directly printed on the PP decorative film by gravure printing, the printing leveling, adhesion and water resistance of subsequent gravure ink can be greatly improved.

[0005] One of the technical solutions of the present invention is to provide a PP decorative film water-based adhesion promoter, which specifically comprises the following:

[0006] 20-30 parts by weight of adhesion promoting resin, 0.05-0.15 parts by weight of wetting agent, 0.01-0.05 parts by weight of defoaming agent, 69.85-79.94 parts by weight of purified water;

[0007] Among them, the adhesion promoter resin is a P[(C12-C18)-co-I]-b-PAA polymer;

[0008] The wetting agent is one or more of alkyl alcohol ammonium salt wetting agents and acrylic copolymer solution wetting agents;

[0009] The defoaming agent is one or more of mineral oil defoaming agents, lower alcohol defoaming agents, and silicone defoaming agents.

[0010] The second technical solution of the present invention lies in providing a preparation method of the above-mentioned aqueous adhesion promoter for PP decorative films, which has the following steps:

[0011] (1) Prepare a chain transfer reagent;

[0012] (2) Prepare a PI-b-PAA diblock copolymer;

[0013] (3) Prepare a P[(C12-C18)-co-I]-b-PAA polymer;

[0014] (4) Mix and stir evenly 20-30 parts by weight of the adhesion promoter resin, 0.05-0.15 parts by weight of the wetting agent, 0.01-0.05 parts by weight of the defoaming agent, and 69.85-79.94 parts by weight of pure water; the adhesion promoter resin is a P[(C12-C18)-co-I]-b-PAA polymer.

[0015] Furthermore, the step of preparing the chain transfer reagent is as follows:

[0016] (1) Stir and dissolve 3.01 g of the precursor, 0.2 g of the azodiisocyanatovaleric acid initiator, 12.51 g of acrylic acid, and 86 g of dioxane thoroughly, purge with nitrogen to remove oxygen for half an hour, react at 80 °C for 2 hours, and then cool the system to room temperature;

[0017] The structural formula of the precursor is: ;

[0018] Among them, Z is an alkylthio group with twelve carbon atoms, and X is an isopropyl acid group;

[0019] (2) Precipitate the chain transfer reagent with cyclohexane and dry it in vacuo to constant weight to obtain the chain transfer reagent.

[0020] Furthermore, the method for preparing the PI-b-PAA diblock copolymer is as follows:

[0021] (1) Dissolve 1.8 g of the above-mentioned chain transfer reagent in 150-200 g of pure water;

[0022] (2) Add 34 - 44.2 g of isoprene, purge with nitrogen to remove oxygen at room temperature, and stir and swell for 1 - 2 h at a speed of 350 rpm;

[0023] (3) After heating to 60 - 70 °C, add 0.02 - 0.03 g of potassium persulfate dissolved in 3 g of pure water to initiate polymerization;

[0024] (4) After reacting for 20 min, slowly inject 0.06 g of NaOH dissolved in 3 g of pure water into the system, maintain the stirring rate of 350 rpm until the conversion rate of isoprene monomer reaches 100%, then the polymerization ends, and continue to stir while keeping warm for 0.5 h to obtain a PI-b-PAA diblock copolymer emulsion.

[0025] Further, the steps for preparing P[(C12 - C18)-co-I]-b-PAA polymer are as follows:

[0026] (1) Mix 200 g of the above PI-b-PAA diblock copolymer emulsion with 40 - 52 g of long-chain alkyl acrylate of C12 - C18, purge with nitrogen and stir for pre-emulsification for 1 - 2 h at room temperature;

[0027] (2) Immerse in a constant temperature water bath at 70 °C, purge with nitrogen to remove oxygen for 30 min, then add 0.02 - 0.04 g of potassium persulfate dissolved in 3 g of pure water to initiate polymerization, stir at 350 rpm until the conversion rate of long-chain alkyl acrylate monomer of C12 - C18 reaches 100%, and then continue to stir while keeping warm for 0.5 - 1 h to obtain a P[(C12 - C18)-co-I]-b-PAA polymer emulsion.

[0028] Further, the wetting agent is one or more of alkyl alcohol ammonium salt wetting agents and acrylic copolymer solution wetting agents.

[0029] Further, the defoaming agent is one or more of mineral oil defoaming agents, lower alcohol defoaming agents, and silicone defoaming agents.

[0030] Further, the conductivity of the pure water is not more than 10 μs / cm at 25 °C.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1. It can be applied to PP decorative films, avoiding the high-cost flame, corona or plasma pretreatment process. After being used on PP decorative films, it is more conducive to the printing of inks, greatly improving the wetting and leveling property, adhesion and water resistance of inks;

[0033] 2. The storage period of the promoter is up to more than two years;

[0034] 3. Using an aqueous system, it is green and environmentally friendly;

[0035] 4. The product has a much better effect in enhancing the adhesion to ink than imported products and lower costs. Description of the Drawings

[0036] Figure 1 It is a printing effect diagram of printing aqueous red ink on a PP decorative film through a KPP gravure proofing machine without pre - coating an adhesion promoter.

[0037] Figure 2 It is a printing effect diagram of printing aqueous red ink on a PP decorative film through a KPP gravure proofing machine after pre - coating the adhesion promoter of Example 1 of the present invention.

[0038] Figure 3 It is a printing effect diagram of printing aqueous yellow ink on a PP decorative film through a KPP gravure proofing machine after pre - coating the adhesion promoter of Example 1 of the present invention.

[0039] Figure 4 It is a printing effect diagram of printing aqueous blue ink on a PP decorative film through a KPP gravure proofing machine after pre - coating the adhesion promoter of Example 1 of the present invention.

[0040] Figure 5 It is a printing effect diagram of printing aqueous black ink on a PP decorative film through a KPP gravure proofing machine after pre - coating the adhesion promoter of Example 1 of the present invention.

[0041] Figure 6 It is a comparison diagram of the effects after printing aqueous ink through a gravure wood grain plate roller after pre - coating the adhesion promoter of Example 1 of the present invention and a commercially available aqueous adhesion promoter. From left to right, the four scale rulers are the leveling effects of the inks on the press for the 1st and 2nd color sequences after pre - coating the adhesion promoter of Example 1, the leveling effects of the inks on the press for the 1st and 2nd color sequences after pre - coating the commercially available adhesion promoter, the leveling effects of the inks on the press for the 3rd and 4th color sequences after pre - coating the adhesion promoter of Example 1, and the leveling effects of the inks on the press for the 3rd and 4th color sequences after pre - coating the commercially available adhesion promoter. Yellow is the 1st color sequence, red is the 2nd color sequence, blue is the 3rd color sequence, and black is the 4th color sequence. Detailed Embodiments

[0042] The following examples are used to further illustrate the present invention. Their purpose is to explain the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, weight parts and weight percentages are used hereinafter.

[0043] The raw materials used in the present invention are all conventional commercially available products unless otherwise specified; the methods used in the present invention are all conventional methods in the art unless otherwise specified.

[0044] The monomer conversion rate was obtained by the gravimetric method. Samples were taken from the reaction system at the set time points, and a 0.5 wt% hydroquinone water / tetrahydrofuran solution was added dropwise to inhibit polymerization. The samples were vacuum dried at a temperature higher than the polymer Tg, and the conversion rate was calculated based on the mass difference before and after drying.

[0045] The particle size and particle size distribution of the adhesion promoter resin were tested on a Malvern ZETASIZER 3000 HAS particle size analyzer at a test temperature of 25 °C.

[0046] The molecular weight and molecular weight distribution of the chain transfer agent and the adhesion promoter resin were determined on a Waters 1525-2414-717 GPC gel permeation chromatography instrument. The eluent was tetrahydrofuran, and narrow distribution polystyrene standards were used for calibration.

[0047] The storage stability of the adhesion promoter resin and the adhesion promoter refers to its standing for 36 days at 60 °C without precipitation or stratification, indicating a storage stability of more than two years.

[0048] After pre-coating the adhesion promoter, the influence on the printing effect of water-based ink was evaluated as follows: Using a KPP gravure proofing machine, at a speed of 40 m / min, the adhesion promoter was printed on the PP decorative film. Then, the water-based ink was printed on the PP decorative film using the KPP gravure proofing machine at a printing speed of 40 m / min and dried at 50 °C. The leveling effect of the printed color patches was observed with the naked eye.

[0049] The evaluation of different adhesion promoters in enhancing the printing effect of water-based ink was as follows: Four-color press-ready ink was prepared by mixing water-based single-color inks (red, yellow, blue, black). Using a gravure wood grain roller proofing machine, at a printing speed of 50 m / min, it was printed on the PP decorative film pre-coated with the adhesion promoter and then dried at 50 °C. The leveling effect of the printed color patches in each color sequence was observed with the naked eye.

[0050] The adhesion test of water-based ink was carried out according to GB / T 13217.7-2009. An adhesion fastness of ≥95% was considered excellent for the water-based ink. The preparation of the test sample was as follows: Using a KPP gravure proofing machine, at a speed of 40 m / min, the adhesion promoter was printed on the PP decorative film. Then, the water-based ink was printed on the PP decorative film using the KPP gravure proofing machine at a printing speed of 40 m / min and dried at 50 °C.

[0051] The water resistance of water-based ink coatings is carried out according to GB1733-1993. After immersion for 100 hours, if there is no fading, gloss reduction, blistering, or shedding, the sample is deemed qualified. The longer the immersion time is without the aforementioned changes, the better the water resistance is. The sample is prepared as follows: After the adhesion promoter is printed on the PP decorative film at a speed of 40m / min using a KPP gravure proofing machine, the water-based ink is printed on the PP decorative film using a KPP gravure proofing machine at a printing speed of 40m / min and then dried at 50°C.

[0052] The water-based ink used above uses the company's self-made PVC furniture film gravure printing water-based ink ("A PVC furniture film gravure printing water-based ink and its preparation method", ZL 201710810616.9).

[0053] The embodiments of the present invention are further described below with reference to a plurality of embodiments.

[0054] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0055] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0056] Example 1

[0057] 1. The preparation method of chain transfer reagent is as follows:

[0058] (1) First, add 3.01 g of precursor, 0.2 g of V501 (azobisisocyanovaleric acid) initiator, 12.51 g of AA (acrylic acid) and 86 g of dioxane into a three-necked round-bottom flask, stir thoroughly to dissolve, pass nitrogen to deoxygenate for half an hour, and then react at 80 °C for 2 hours. The AA conversion rate is close to 100%. Then cool the system to room temperature;

[0059] The structural formula of the precursor is: ;

[0060] Wherein, Z is an alkylthio group having twelve carbon atoms, and X is an isopropanoic acid group; GPC detection shows that the molecular weight of the chain transfer agent is 1876 g / mol (theoretical molecular weight 1804 g / mol), and the molecular weight distribution is 1.11. The measured molecular weight is consistent with the theoretical molecular weight, and the molecular weight distribution is also narrow.

[0061] Preparation of 2.PI-b-PAA diblock copolymer:

[0062] In a 1 L steel autoclave (Weihai Automatic Control Co., Ltd., Shandong), 1.8 g of a chain transfer agent was dissolved in 150 g of pure water (the initial pH value of the aqueous phase was about 3.0). Then, 34 g of isoprene (Sinopharm Group) was added to the aqueous phase. Nitrogen was passed through to remove oxygen at room temperature, and the mixture was stirred at a speed of 350 rpm for 1 h for swelling. Then, the temperature was raised to 60 °C, and 0.02 g of potassium persulfate (Sinopharm Group) (dissolved in 3 g of pure water) was added to initiate polymerization. After 20 min of reaction, 0.06 g of NaOH (dissolved in 3 g of pure water) was slowly injected into the system, and the reaction continued until polymerization was completed. During the reaction process, the stirring rate was maintained at 350 rpm, and samples were taken regularly for testing and analysis. After the conversion rate of isoprene monomer reached 100%, stirring was continued for 0.5 h while maintaining the temperature to obtain a PI-b-PAA diblock copolymer emulsion.

[0063] 3.Preparation of P(C18-co-I)-b-PAA "comb" polymer:

[0064] Take 200 g of the above PI-b-PAA diblock copolymer emulsion into a 100 mL four-necked flask, and then add 40 g of octadecyl acrylate (Jiangsu Bost Chemical Technology Co., Ltd.). Nitrogen was passed through and stirred at room temperature for 1 h for pre-emulsification. Then, the four-necked flask was immersed in a 70 °C constant temperature water bath. After nitrogen was passed through to remove oxygen for 30 min, 0.02 g of potassium persulfate (Sinopharm Group) (dissolved in 3 g of pure water) was added to initiate polymerization. During the reaction process, the stirring rate was maintained at 350 rpm, and samples were taken regularly for testing and analysis. After the conversion rate of octadecyl acrylate (Jiangsu Bost Chemical Technology Co., Ltd.) monomer reached 100%, stirring was continued for 0.5 h while maintaining the temperature to obtain a P(C18-co-I)-b-PAA "comb" polymer emulsion.

[0065] 4.Preparation of adhesion promoter:

[0066] 20 parts of P(C18-co-I)-b-PAA "comb" polymer emulsion adhesion promoter resin, 0.05 part of ANTI-TERRA-250 (BYK), 0.01 part of DAPPO ® DF 3163 (Dekking) and 79.94 parts of pure water were stirred and mixed evenly, and then filtered and discharged to obtain the adhesion promoter.

[0067] Without pre-coating the adhesion promoter, aqueous red ink was printed on the PP decorative film by a KPP gravure proofing machine Figure 1After applying the adhesion promoter in Precoating Example 1, the aqueous red ink was printed on the PP decorative film through a KPP gravure proofing machine. Figure 2 As can be seen from the comparison, for the PP decorative film without precoating the adhesion promoter, the printing leveling property of the red ink was very poor, and a large number of shrinkage holes appeared, indicating that the water-based ink could not effectively wet and level the substrate; while after precoating the adhesion promoter of Example 1 of the present invention, the printing leveling of the red ink was significantly improved, and there were no printing defects such as shrinkage holes and "orange peel". From the attached Figures 3 - 5 It can be seen that for other color inks, after precoating the aqueous adhesion promoter of the present invention, their printing leveling properties were also excellent (the surface scratches were caused by film-like friction). From Figure 6 It can be seen that after precoating a commercially available aqueous adhesion promoter, the overall wettability of the in-machine mixed ink was good, but there were still some printing defect phenomena such as "orange peel" and "water ripple", while the system using the adhesion promoter of the present invention had no such defect phenomena. The above results show that using the aqueous adhesion promoter of the present invention can solve the defects of poor wetting and leveling of traditional water-based inks on untreated PP decorative films; compared with commercially available aqueous adhesion promoters, the aqueous adhesion promoter of the present invention has a more significant effect on improving the printing leveling property of water-based inks.

[0068] Example 2

[0069] The preparation method of the chain transfer reagent was the same as that in Example 1.

[0070] 1. Preparation of PI-b-PAA diblock copolymer:

[0071] In a 1L steel autoclave (Weihai Automatic Control Co., Ltd., Shandong), 1.8 g of the chain transfer reagent was dissolved in 180 g of pure water (the initial pH value of the aqueous phase was about 3.0). Then 40.8 g of isoprene (Sinopharm Group) was added to the aqueous phase, and nitrogen was passed through to remove oxygen at room temperature, and it was stirred and swollen at a speed of 350 rpm for 2 h. Then it was heated to 70 °C and 0.03 g of potassium persulfate (Sinopharm Group) (dissolved in 3 g of pure water) was added to initiate polymerization. After reacting for 20 min, 0.06 g of NaOH (dissolved in 3 g of pure water) was slowly injected into the system, and the reaction continued until polymerization was completed. During the reaction process, the stirring rate of 350 rpm was maintained, and samples were taken regularly for test analysis. After the conversion rate of the isoprene monomer reached 100%, it was continuously stirred at a constant temperature for 1 h to obtain a PI-b-PAA diblock copolymer emulsion.

[0072] 2. Preparation of P(C18-co-I)-b-PAA "comb" type polymer:

[0073] Take 200 g of the above PI-b-PAA diblock copolymer emulsion into a 100 mL four-necked flask, then add 50 g of octadecyl acrylate (Jiangsu Bost Chemical Technology Co., Ltd.), and pre-emulsify by stirring under nitrogen at room temperature for 2 h. Then immerse the four-necked flask in a constant temperature water bath at 70 °C, deoxygenate by passing nitrogen for 30 min, and then add 0.04 g of potassium persulfate (Sinopharm Group Co., Ltd.) (dissolved in 3 g of pure water) to initiate the polymerization. During the reaction process, maintain a stirring rate of 350 rpm, take samples regularly for test analysis. After the monomer conversion rate of octadecyl acrylate (Jiangsu Bost Chemical Technology Co., Ltd.) reaches 100%, continue to stir at a constant temperature for 1 h to obtain the P(C18-co-I)-b-PAA "comb"-type polymer emulsion.

[0074] 3. Preparation of the adhesion promoter:

[0075] Mix 25 parts of the adhesion promoting resin of the P(C18-co-I)-b-PAA "comb"-type polymer emulsion, 0.15 part of ANTI-TERRA-250 (BYK Co., Ltd.), 0.03 part of DAPPO ® DF 3163 (Dekang Co., Ltd.) and 74.82 parts of pure water evenly by stirring, and then filter and discharge to obtain the adhesion promoter.

[0076] Example 3:

[0077] The preparation method of the chain transfer agent is the same as that in Example 1.

[0078] 1. Preparation of the PI-b-PAA diblock copolymer:

[0079] In a 1 L steel autoclave (Shandong Weihai Automatic Control Co., Ltd.), dissolve 1.8 g of the chain transfer agent in 200 g of pure water (the initial pH value of the aqueous phase is about 3.0). Then add 44.2 g of isoprene (Sinopharm Group Co., Ltd.) to the aqueous phase, deoxygenate by passing nitrogen at room temperature, stir and swell at a speed of 350 rpm for 2 h, then raise the temperature to 70 °C and add 0.03 g of potassium persulfate (Sinopharm Group Co., Ltd.) (dissolved in 3 g of pure water) to initiate the polymerization. After 20 min of the reaction, slowly inject 0.06 g of NaOH (dissolved in 3 g of pure water) into the system, and continue the reaction until the polymerization ends. During the reaction process, maintain a stirring rate of 350 rpm, take samples regularly for test analysis. After the monomer conversion rate of isoprene reaches 100%, continue to stir at a constant temperature for 1 h to obtain the PI-b-PAA diblock copolymer emulsion.

[0080] 2. Preparation of the P(C18-co-I)-b-PAA "comb"-type polymer:

[0081] Take 200 g of the above PI-b-PAA diblock copolymer emulsion into a 100 mL four-necked flask, then add 52 g of dodecyl acrylate (Jiangsu Bost Chemical Technology Co., Ltd.), and stir and pre-emulsify under nitrogen at room temperature for 2 h. Then immerse the four-necked flask in a 70 °C constant temperature water bath, deoxygenate under nitrogen for 30 min, and then add 0.04 g of potassium persulfate (Sinopharm Group Co., Ltd.) (dissolved in 3 g of pure water) to initiate polymerization. During the reaction process, maintain a stirring rate of 350 rpm, regularly sample for testing and analysis. After the monomer conversion rate of dodecyl acrylate (Jiangsu Bost Chemical Technology Co., Ltd.) reaches 100%, continue to stir at a constant temperature for 1 h to obtain the P(C18-co-I)-b-PAA "comb"-type polymer emulsion.

[0082] 3. Preparation of adhesion promoter:

[0083] Mix 30 parts of the adhesion promoting resin of P(C18-co-I)-b-PAA "comb"-type polymer emulsion, 0.1 part of ANTI-TERRA-250 (BYK Co., Ltd.), 0.05 part of DAPPO ® DF 3163 (Dekking Co., Ltd.) and 69.85 parts of pure water, stir and mix evenly, then filter and discharge to obtain the adhesion promoter.

[0084] Table 1. Performance data of adhesion promoting resin in Examples 1-3

[0085]

[0086] Table 2. Performance data of adhesion promoters and comparative samples in Examples 1-3

[0087] Example 1 Example 2 Example 3 Commercially available waterborne adhesion promoter Commercially available oil-based chlorinated polypropylene Corona pretreatment of the PP decorative film No pretreatment of the PP decorative film Printing leveling property Good Good Good Slightly poor Good Good Very poor Adhesion 100% 98% 100% 81% 98% 93% 0% Water resistance Qualified Qualified Qualified Unqualified Qualified Qualified Unqualified Storage stability (> two years) Passed Passed Passed Passed Passed - -

[0088] As can be seen from Table 2, compared with the case where no pretreatment is performed on the PP decorative film, after pre-coating with the aqueous adhesion promoter of the present invention, the adhesion and water resistance of the water-based ink have been greatly improved, reaching or even slightly exceeding the pretreatment process effects of pre-coated oily chlorinated polypropylene and corona treatment, and being superior to the effects of commercially available aqueous adhesion promoters, and are expected to be widely applied in the field of PP decorative films.

[0089] The above embodiments have detailedly illustrated the structure, characteristics and action effects of the present invention. The above are only the preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modified into equivalent embodiments with equivalent changes, still within the scope covered by the specification, shall fall within the protection scope of the present invention.

Claims

1. A preparation method of an aqueous adhesion promoter for PP decorative film, characterized in that, The following steps are involved: (1) preparing a chain transfer reagent; the steps of preparing the chain transfer reagent are: 1) The precursor, azobisisocyanovaleric acid initiator, acrylic acid and dioxane were fully stirred and dissolved, nitrogen was passed through for half an hour to deoxygenate, and then the reaction was carried out at 80°C for 2 hours, and then the system was cooled to room temperature; The structural formula of the precursor is as follows: ; Wherein, Z is an alkylthio group having twelve carbon atoms, and X is an isopropanoyl group; 2) precipitating the chain transfer reagent with cyclohexane and vacuum drying to constant weight to obtain the chain transfer reagent; (2) Preparing a PI-b-PAA diblock copolymer; the method for preparing the PI-b-PAA diblock copolymer is: 1) Dissolve the above chain transfer reagent in pure water; 2) Add isoprene, pass nitrogen to deoxygenate at room temperature, and stir at 350 rpm to swell for 1-2 hours; 3) After heating to 60-70°C, add 0.02-0.03g potassium persulfate dissolved in 3g pure water to initiate polymerization; 4) After reacting for 20 minutes, 0.06 g of NaOH dissolved in 3 g of pure water was slowly injected into the system, and the stirring rate was maintained at 350 rpm until the isoprene monomer conversion rate reached 100%. The polymerization was completed and the stirring was continued for 0.5 h to obtain a PI-b-PAA diblock copolymer emulsion; (3) Preparing a P[(C12-C18)-co-I]-b-PAA polymer; the preparation steps of the P[(C12-C18)-co-I]-b-PAA polymer are as follows: 1) Mix 200 g of the above PI-b-PAA diblock copolymer emulsion and 40-52 g of C12-C18 long alkyl acrylate, and pre-emulsify for 1-2 h at room temperature with nitrogen stirring; 2) Immerse in a 70°C constant temperature water bath, pass nitrogen to deoxygenate for 30 minutes, then add 0.02-0.04g potassium persulfate dissolved in 3g pure water to initiate polymerization, stir at 350rpm until the conversion rate of C12-C18 long alkyl acrylate monomer reaches 100%, continue to keep warm and stir for 0.5-1h to obtain P[(C12-C18)-co-I]-b-PAA polymer emulsion; (4) 20-30 parts by weight of an adhesion-promoting resin, 0.05-0.15 parts by weight of a wetting agent, 0.01-0.05 parts by weight of a defoaming agent, and 69.85-79.94 parts by weight of purified water are mixed and stirred uniformly; the adhesion-promoting resin is a P[(C12-C18)-co-I]-b-PAA polymer.

2. The preparation method according to claim 1, characterized in that, The amounts of raw materials used in the step of preparing the chain transfer agent are: 3.01 g of the precursor, 0.2 g of the initiator azobisisocyanovaleric acid, 12.51 g of acrylic acid and 86 g of dioxane.

3. The preparation method according to claim 1, wherein In the step of preparing the PI-b-PAA diblock copolymer, the masses of the chain transfer reagent and the purified water in step 1 are 1.8 g and 150-200 g respectively; the mass of the isoprene in step 2 is 34-44.2 g.

4. The preparation method according to claim 1, wherein, The wetting agent in step 4 is one or more of an alkyl alcohol ammonium salt wetting agent and an acrylic copolymer solution wetting agent.

5. The preparation method according to claim 1, characterized in that, The defoamer described in step 4 is one or more of mineral oil defoamers, lower alcohol defoamers, and silicone defoamers.

6. The preparation method according to claim 1, characterized in that, The conductivity of the purified water is not greater than 10 μs / cm at 25°C.

7. A waterborne adhesion promoter for PP decorative films prepared by the method according to claim 1.

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