High-viscosity self-adhesive label paper and preparation method thereof

Abstract

The invention relates to the technical field of label paper, in particular to high-viscosity self-adhesive label paper and a preparation method thereof. The adhesive layer of the label paper is constructed by the following steps: performing sodium chloroacetate carboxymethylation and itaconic acid aza-Michael addition dual modification on branched polyethyleneimine, grafting dopamine to introduce a catechol functional group and form a coordination node with ferric iron, and compounding with a polyvinyl alcohol-borate dynamic reversible network to obtain the label paper. And finally, carrying out electrostatic compounding with poly (diallyldimethylammonium chloride) at an isoelectric point. According to the design, the adhesive layer has high peel strength and aging resistance in a dry state, can be quickly softened after meeting water and can be completely removed in an interface debonding manner, so that the residual adhesive rate and the substrate damage risk are remarkably reduced, and the problem that high adhesion and removability are difficult to consider at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of label paper technology, and in particular to a high-adhesion self-adhesive label paper and its preparation method. Background Technology

[0002] As a core consumable in modern packaging, logistics, and labeling, the performance of self-adhesive labels directly affects the reliability of information adhesion and the convenience of use. With the expansion of application scenarios, the performance requirements for label paper have evolved from simply ensuring strong adhesion to achieving a delicate balance between high adhesion strength, broad substrate adaptability, and ease of removal. Traditional high-tack self-adhesive labels, in pursuit of initial peel strength, generally employ tackifying resins (such as rosin and terpene resins) or introduce irreversible crosslinking agents (such as isocyanates and epoxy resins) to modify the adhesive.

[0003] However, while strategies relying on tackifying resins can improve adhesion to common substrates (such as cardboard and stainless steel), their tackification mechanisms often result in insufficient cohesive strength of the adhesive layer. During peeling, especially from substrates with low surface energy or weak polarity such as glass and polyethylene terephthalate, cohesive failure is highly likely, leaving a large amount of residual adhesive on the substrate surface. This not only affects aesthetics but also makes subsequent cleaning extremely difficult. On the other hand, while irreversible chemical cross-linking curing methods can significantly enhance adhesive layer cohesion, the resulting three-dimensional network structure is too dense and stable. This makes it difficult to peel off the label completely after use, and forced removal may damage the surface of the object due to the enormous interfacial stress, such as scratching the plastic substrate or peeling the paint, completely deviating from the original design intent of removable labels.

[0004] At a deeper level, the predicament of existing technologies lies in their tendency to focus on constructing a single, intensified mechanism of action. Whether through physical adhesion or chemical cross-linking, the goal is to infinitely enhance adhesion or cohesion, while neglecting the dynamic control required for the contradictory processes of adhesion establishment and interfacial debonding. In a dry environment, the adhesive needs to fully wet and firmly adhere to the substrate; however, when removal is required (especially through gentle methods such as water immersion), a controllable failure of the adhesive layer, primarily driven by interfacial separation, is desired. Existing technologies struggle to achieve this environmentally responsive performance switching within the same system. Their adhesive layer structures lack the necessary dynamism and reversibility, making high adhesion and easy removal mutually exclusive performance goals. This severely restricts their application in fields with stringent requirements for clean removal, such as high-end labeling, recyclable packaging, and temporary protection of precision electronic components. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a high-adhesion self-adhesive label paper and its preparation method, so as to solve the problems of existing high-adhesion self-adhesive label papers relying on tackifying resins or irreversible cross-linking, resulting in peeling residue, weak adhesion to low surface energy substrates, and easy damage to the substrate during removal, making it difficult to achieve both high adhesion and removability.

[0006] To achieve the above objectives, the present invention provides a high-adhesion self-adhesive label paper, comprising a release liner, an adhesive layer disposed on the release liner, and a face material covering the adhesive layer; the adhesive layer is prepared from the following raw materials in parts by mass: 100 parts branched polyethyleneimine, 40-80 parts sodium chloroacetate, 20-60 parts itaconic acid, 3-5 parts dopamine hydrochloride, 0.2-0.45 parts ferric chloride hexahydrate, 90-110 parts 10% polyvinyl alcohol aqueous solution, 0.8-1.5 parts sodium tetraborate decahydrate, 8-15 parts sodium chloride, 40-60 parts 20% polydiallyl dimethyl ammonium chloride aqueous solution, and 8-15 parts glycerol.

[0007] Preferably, the branched polyethyleneimine is introduced into an iminodiacetic acid type carboxyl structural unit by sodium chloroacetate carboxylation, and then into an itaconic acid type dicarboxyl structural unit by itaconic acid aza-Michael addition, to obtain carboxylated branched polyethyleneimine.

[0008] Preferably, the isoelectric point of the carboxylated branched polyethyleneimine corresponds to a pH value of 7.2-8.6, wherein the pH value corresponding to the isoelectric point is the pH value when the absolute value of the zeta potential is ≤2mV when measured at 25°C.

[0009] Preferably, the carboxylated branched polyethyleneimine is grafted with dopamine at its carboxyl site to introduce a catechol functional group.

[0010] Preferably, the catechol functional group forms a coordination node with ferric iron.

[0011] Preferably, the polyvinyl alcohol and the sodium tetraborate decahydrate form a reversible network, and the glycerol competitively regulates the reversible network.

[0012] Preferably, the branched polyethyleneimine has a weight-average molecular weight of 20,000-30,000.

[0013] Preferably, the weight-average molecular weight of the polydiallyl dimethyl ammonium chloride is 200,000-350,000.

[0014] Preferably, the polyvinyl alcohol has a weight-average molecular weight of 13,000-23,000 and a degree of alcoholysis of 87%-89%.

[0015] Preferably, the release liner is glassine silicone oil release liner with a basis weight of 60 g / m³.2 The thickness is 54μm; the face material is a semi-gloss coated paper face material with a basis weight of 80g / m³. 2 .

[0016] Preferably, the wet coating amount of the adhesive layer is 45-55 g / m². 2 The material is dried at 30-35℃ for 10-12 hours to form a dry adhesive layer; the surface material and the dry adhesive layer are laminated by pressing them together three times under a pressure of 300kPa using a rubber roller.

[0017] Furthermore, the present invention also provides a method for preparing high-adhesion self-adhesive label paper, comprising the following steps:

[0018] (1) Using branched polyethyleneimine as raw material, a carboxylated branched polyethyleneimine solution was prepared by carboxylation with sodium chloroacetate and a azirmi-Michael addition reaction with itaconic acid;

[0019] (2) Adjust the pH of the carboxylated branched polyethyleneimine solution to the pH value corresponding to the isoelectric point;

[0020] (3) Under nitrogen protection and at pH 5-6, dopamine is grafted onto the carboxylated branched polyethyleneimine through a carbodiimine system to obtain a carboxylated branched polyethyleneimine solution containing catechol functional groups.

[0021] (4) Adjust the solution obtained in step (3) to acidity and add ferric salt to form an acidic pre-coordination system, and then raise the pH to form a gel containing ferric coordination nodes;

[0022] (5) Add polyvinyl alcohol aqueous solution, borate and sodium chloride to the adhesive solution obtained in step (4) in sequence, adjust the pH to the pH value corresponding to the isoelectric point, and then add polydiallyl dimethyl ammonium chloride aqueous solution for electrostatic composite. Then add glycerol and degas to obtain a coatable adhesive solution.

[0023] (6) The coatable adhesive is applied to the release liner and dried to form a dry adhesive layer. Then the face material is laminated onto the dry adhesive layer and pressed together to obtain a high-adhesion self-adhesive label.

[0024] The beneficial effects of this invention are:

[0025] First, this invention introduces carboxyl functional groups with tunable density and type into the molecular chain of branched polyethyleneimine through a combination of sodium chloroacetate carboxylation and itaconic acid aza-Michael addition. This design allows the isoelectric point of the modified polymer to be precisely controlled to near neutral, laying an ideal charge-matching foundation for its subsequent electrostatic composite with positively charged polydiallyldimethylammonium chloride. Composite formation near the isoelectric point effectively avoids hard flocculation and precipitation, instead forming a uniform, stable, coatable co-depositional phase. This phase provides excellent initial tack and cohesive strength in the dry state through ion pairing and chain segment entanglement, while upon contact with water, the ion pairs can be rapidly hydrated and shielded, thereby achieving overall softening and rapid removal of the adhesive layer, essentially reconciling the contradiction between high adhesion and removability.

[0026] Secondly, by grafting dopamine onto specific carboxyl sites of carboxylated branched polyethyleneimine, catechol functional groups with strong coordination and adsorption capabilities were successfully introduced. These catechol groups can not only form various interfacial interactions (such as hydrogen bonds and coordination bonds) with low surface energy substrates such as glass and polyethylene terephthalate, significantly improving the adhesion and reliability of labels on these difficult-to-adhere substrates, but also their inherent reversible coordination characteristics facilitate the controllable dissociation of the interfacial layer during removal, thereby minimizing the risk of physical damage to the substrate surface during peeling while achieving high adhesion.

[0027] Furthermore, a sequential approach of first pre-coordinating with acid and then enhancing with increased pH is employed to introduce ferric ions, enabling them to form stable coordination nodes with the catechol functional groups on the polymer chain. This strategy effectively avoids the problem of easy hydrolysis and precipitation of ferric ions under alkaline conditions, ensuring the effective construction and uniform distribution of coordination nodes. These dynamic metal coordination bonds act as physical crosslinking points in the dry state, greatly enhancing the shear resistance and cohesive strength of the adhesive layer, thereby ensuring the adhesion reliability of the label under harsh conditions such as logistics handling, and exhibiting excellent resistance to high temperature and high humidity aging.

[0028] Finally, this invention creatively constructs a dynamic reversible network of polyvinyl alcohol (PVA) and borate, and competitively regulates it by adding glycerol after electrostatic compounding. This design creates a partitioned network structure: the backbone network composed of PVA and borate provides the necessary film-forming properties and skeletal strength; while glycerol, as a small molecule regulator, fine-tunes the tightness of the reversible network by competing with borate for coordination. This structure allows the adhesive layer to remain tight and highly viscous in the dry state, while in an immersion environment, water can quickly penetrate and preferentially interact with components such as glycerol and borate, causing the entire reversible network to swell and relax. This, combined with the dissociation of the electrostatic compounding system, drives the adhesive layer to quickly and completely separate from the substrate in a manner dominated by interfacial debonding, thereby achieving extremely low residual adhesive content and excellent substrate protection. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0030] The branched polyethyleneimine used in the examples and comparative examples was Merck (Sigma-Aldrich) product number 408727, a viscous liquid with a weight-average molecular weight of approximately 25,000, a number-average molecular weight of approximately 10,000, a water content of ≤1%, and a density of approximately 1.030 g / mL (25°C). The polydiallyldimethylammonium chloride used was Merck (Sigma-Aldrich) product number 409022, an aqueous solution with a mass fraction of 20%, a weight-average molecular weight of 200,000-350,000, and a density of approximately 1.04 g / mL (25°C). The polyvinyl alcohol used was Merck (Sigma-Aldrich) product number 363170, with a weight-average molecular weight of 13,000-23,000 and a degree of hydrolysis of 87-89%. The release paper was Avery. Dennison Materials Group AG313 White Glassine Silicone Release Paper, Basis Weight 60g / m³ 2 Thickness 54μm; the face stock is UPM Raflatac Raflacoat Plus-FSC semi-gloss coated paper with a basis weight of 80g / m². 2 .

[0031] Example 1:

[0032] Step 1: Add 800g of deionized water to a container and place it in an ice-water bath. Start stirring at 300rpm, then add 200g of sodium hydroxide solid in batches, controlling the solution temperature ≤35℃ and stirring until completely dissolved, to obtain 1000g of a 20% sodium hydroxide aqueous solution; Add 730g of deionized water to another container and place it in an ice-water bath. Start stirring at 300rpm, then slowly add 270g of hydrochloric acid (37% by mass), controlling the solution temperature ≤35℃ and stirring until homogeneous, to obtain 100g of a 10% hydrochloric acid aqueous solution. 0g; Add 400g of deionized water to a 1L reactor, turn on mechanical stirring at 600rpm, add 100g of branched polyethyleneimine, control the temperature at 25℃ and stir for 60min to obtain 500g of branched polyethyleneimine aqueous solution with a mass fraction of 20%; then add 180g of deionized water to another container, heat to 90℃ and stir at 400rpm, add 20g of polyvinyl alcohol, keep at 90℃ and stir for 60min until completely dissolved, then cool to 25℃ to obtain 200g of polyvinyl alcohol aqueous solution with a mass fraction of 10%;

[0033] Step 2: Dilute 500g of a 20% (w / w) branched polyethyleneimine aqueous solution with 200g of deionized water. Heat to 50℃ and stir at 600rpm. Adjust the pH to 10 using a 10% (w / w) hydrochloric acid aqueous solution. Then, add 60g of sodium chloroacetate in four portions (15g each time, 10min apart), maintaining the pH between 9.5-10.5 with a 20% (w / w) sodium hydroxide aqueous solution during the addition process. Continue the reaction at 50℃ for 4 hours. After the reaction, cool to 25℃. Then add 40g of itaconic acid, heat to 40℃ and stir at 500rpm. The pH was adjusted to 9 using a 20% sodium hydroxide aqueous solution, and the mixture was reacted at 40°C for 8 hours. After cooling to 25°C, the pH was adjusted to 7 using a 10% hydrochloric acid aqueous solution. The solution was then transferred to a dialysis bag for desalting. A molecular weight cutoff of 3500 was selected for the dialysis bag. The solution inside the bag was placed in 5000g of deionized water as an external solution and dialyzed for 12 hours. The external solution was replaced every 4 hours with 5000g of deionized water each time, for a total of 3 replacements. After dialysis, the solution inside the bag was collected and concentrated under reduced pressure at 45°C. The water was continuously evaporated until the total mass of the solution was 600g, yielding a carboxylated branched polyethyleneimine aqueous solution.

[0034] Step 3: Take 1g of carboxylated branched polyethyleneimine aqueous solution and add it to 99g of deionized water to prepare 100g of test solution with a mass fraction of 1%. Under the condition of 25℃, adjust the pH dropwise with 20% sodium hydroxide aqueous solution and 10% hydrochloric acid aqueous solution respectively and test the zeta potential. Record the pH corresponding to the absolute value of the zeta potential ≤2mV as the pH value corresponding to the isoelectric point. In this example, the pH value corresponding to the isoelectric point is measured to be 8. Then, use 20% sodium hydroxide aqueous solution and 10% hydrochloric acid aqueous solution to adjust the pH to 8 precisely to obtain the carboxylated branched polyethyleneimine solution after the isoelectric point is adjusted.

[0035] Step 4: Under nitrogen protection, dilute the carboxylated branched polyethyleneimine solution prepared in Step 3 with 200g of deionized water, stir at 600rpm and control the temperature at 25℃, and add 1g of sodium metabisulfite; adjust the pH to 5 using a 10% hydrochloric acid aqueous solution; add 800mg of N-hydroxysuccinimide and stir for 10min, then add 1300mg of sodium metabisulfite. 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was stirred for 30 min to activate the carboxyl group; then 4000 mg of dopamine hydrochloride was added at once and the mixture was stirred at 600 rpm for 6 h. During the reaction, the pH was maintained at 5-6 using a 20% sodium hydroxide aqueous solution. After the reaction, the solution was dialyzed in 5000 g of deionized water for 12 h. The external solution was replaced every 4 h with 5000 g of deionized water each time, for a total of 3 times. After dialyzing, the solution was concentrated under reduced pressure at 45 °C to a total mass of 650 g to obtain a carboxylated branched polyethyleneimine solution containing catechol functional groups.

[0036] Step 5: Take the carboxylated branched polyethyleneimine solution containing catechol functional groups prepared in Step 4, add 100g of deionized water to dilute and stir at 800rpm. Adjust the pH to 4 using a 10% hydrochloric acid aqueous solution. Add 300mg of ferric chloride hexahydrate and continue stirring for 15min to form an acidic pre-coordinated system. Then, raise the pH to 8 using a 20% sodium hydroxide aqueous solution and continue stirring for 15min to obtain a gel containing ferric coordination nodes. Add 100g of polyvinyl alcohol aqueous solution and stir for 10min. Add 1000mg of sodium tetraborate. Add the decahydrate and continue stirring for 20 min; add 10 g of sodium chloride and continue stirring for 10 min, then adjust the pH back to 8 using a 20% sodium hydroxide aqueous solution and a 10% hydrochloric acid aqueous solution; then add 50 g of polydiallyldimethylammonium chloride aqueous solution (20% by mass) dropwise over 30 min while stirring at 800 rpm, and continue stirring for 30 min after the addition is complete to obtain a high-viscosity transferable adhesive solution; then add 10 g of glycerol and stir at 300 rpm for 10 min, then let stand for 30 min to remove bubbles to obtain a coatable adhesive solution;

[0037] Step 6: Cut 60g release paper (Avery Dennison AG313, area 1m²) 2 Lay the paper on the coating table, weigh out 50g of coatable adhesive and apply it evenly to the surface of the release liner using a scraper to form a wet adhesive layer (corresponding to a wet coating amount of 50g / m²). 2 The adhesive layer was then dried in a 30°C hot air oven for 12 hours to obtain the dry adhesive layer; 80g of the surface material (UPM Raflatac Raflacoat Plus-FSC, area 1m²) was cut. 2 The adhesive is applied to the dry adhesive layer and then pressed back and forth three times with a rubber roller at a pressure of 300 kPa to obtain a high-adhesion self-adhesive label.

[0038] Example 2:

[0039] Compared with Example 1, the difference in this example is as follows: In step 4, 1000 mg of N-hydroxysuccinimide is added and stirred for 10 min, then 1625 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is added and stirred for 30 min to activate the carboxyl group. Then, 5000 mg of dopamine hydrochloride is added at once and stirred at 600 rpm for 6 h. In step 5, 450 mg of ferric chloride hexahydrate is added and stirred for 15 min to form an acidic pre-coordinated system. 1200 mg of sodium tetraborate decahydrate is added and stirred for 20 min. 60 g of polydiallyldimethylammonium chloride aqueous solution (20% by mass) is added dropwise. After the dropwise addition is completed, stirring is continued for 30 min. Then, 8 g of glycerol is added and stirred at 300 rpm for 10 min. In step 6, 55 g of coatable adhesive is weighed and a wet adhesive layer is formed (corresponding to a wet coating amount of 55 g / m). 2 The sample was placed in a 35°C hot air oven and dried for 10 hours. All other conditions were the same as in Example 1.

[0040] Example 3:

[0041] Compared with Example 1, the difference in this example is as follows: In step 2, 80g of sodium chloroacetate was added in four portions (20g each time, 10min apart); in step 3, the pH value corresponding to the isoelectric point was measured to be 7.6, and then the pH of the remaining solution in step 2 was precisely adjusted to 7.6; in step 5, 110g of polyvinyl alcohol aqueous solution was added and stirred for 10min, 1500mg of sodium tetraborate decahydrate was added and stirred for another 20min, 8g of sodium chloride was added and stirred for another 10min, and 45g of polydiallyldimethylammonium chloride aqueous solution (20% by mass) was added dropwise, and after the dropwise addition was completed, stirring was continued for 30min, and then 15g of glycerol was added and stirred at 300rpm for 10min. The remaining conditions were the same as in Example 1.

[0042] Example 4:

[0043] Compared with Example 1, the difference in this example is as follows: 60g of itaconic acid was added in step 2; the pH value corresponding to the isoelectric point was measured to be 7.2 in step 3, and the pH of the remaining solution in step 2 was then precisely adjusted to 7.2; in step 4, 900mg of N-hydroxysuccinimide was added and stirred for 10min, followed by the addition of 1460mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and stirring for 30min to activate the carboxyl group, followed by the addition of 4500mg of dopamine hydrochloride and stirring at 600rpm for 6h; in step 5, 350mg of ferric chloride hexahydrate was added and stirred for 15min to form an acidic pre-coordinated system, followed by the addition of 12g of sodium chloride and stirring for 10min, and then 55g of polydiallyldimethylammonium chloride aqueous solution (20% by mass) was added dropwise, and stirring was continued for 30min after the dropwise addition was completed. The remaining conditions were the same as in Example 1.

[0044] Example 5:

[0045] Compared with Example 1, the difference in this example is as follows: In step 2, 40g of sodium chloroacetate was added in four portions (10g each time, 10min apart), followed by the addition of 20g of itaconic acid; in step 3, the pH value corresponding to the isoelectric point was measured to be 8.6, and then the pH of the remaining solution in step 2 was precisely adjusted to 8.6; in step 4, 600mg of N-hydroxysuccinimide was added and stirred for 10min, followed by the addition of 975mg of... 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was stirred for 30 min to activate the carboxyl group. Then, 3000 mg of dopamine hydrochloride was added in one go and the mixture was stirred at 600 rpm for 6 h. In step 5, 200 mg of ferric chloride hexahydrate was added and stirred for 15 min to form an acidic pre-coordinated system. 90 g of polyvinyl alcohol aqueous solution was added and stirred for 10 min. 800 mg of sodium tetraborate decahydrate was added and stirred for 20 min. 15 g of sodium chloride was added and stirred for 10 min. 40 g of polydiallyldimethylammonium chloride aqueous solution (20% by mass) was added dropwise. After the dropwise addition was complete, stirring was continued for 30 min. Then, 12 g of glycerol was added and stirred at 300 rpm for 10 min. In step 6, 45 g of the coatable adhesive was weighed to form a wet adhesive layer (corresponding to a wet coating amount of 45 g / m²). 2 The remaining conditions are the same as in Example 1.

[0046] Comparative Example 1:

[0047] The difference from Example 1 is that 40g of itaconic acid is not added in step 2 (the itaconic acid aza-Michael addition reaction is not carried out), and the other conditions are the same as in Example 1.

[0048] Comparative Example 2:

[0049] The difference from Example 1 is that 60g of sodium chloroacetate is not added in step 2 (sodium chloroacetate carboxymethylation reaction is not carried out), and the other conditions are the same as in Example 1.

[0050] Comparative Example 3:

[0051] The difference from Example 1 is that: after adding 10g of sodium chloride in step 5 and stirring for 10min, the pH is adjusted back to 7 using a 20% sodium hydroxide aqueous solution and a 10% hydrochloric acid aqueous solution. Then, 50g of polydiallyldimethylammonium chloride aqueous solution (20% by mass) is added dropwise, and the pH is maintained at 7 during the dropwise addition and subsequent stirring. The other conditions are the same as in Example 1.

[0052] Comparative Example 4:

[0053] The difference from Example 1 is that 4000 mg of dopamine hydrochloride is not added in step 4, while the other conditions are the same as in Example 1.

[0054] Comparative Example 5:

[0055] The difference from Example 1 is that 1g of sodium metabisulfite is not added in step 4, while the other conditions are the same as in Example 1.

[0056] Comparative Example 6:

[0057] The difference from Example 1 is that in step 5, the pH is not adjusted to 4 and acidic pre-combination is not performed. Instead, after dilution and stirring at 800 rpm, the pH is directly adjusted to 8 using a 20% sodium hydroxide aqueous solution. Then, 300 mg of ferric chloride hexahydrate is added and stirring is continued for 15 min. The other conditions are the same as in Example 1.

[0058] Comparative Example 7:

[0059] The difference from Example 1 is that 1000 mg of sodium tetraborate decahydrate is not added in step 5, while the other conditions are the same as in Example 1.

[0060] Comparative Example 8:

[0061] The difference from Example 1 is that in step 5, 10g of glycerol is added and stirred at 300rpm for 10min before adding the aqueous solution of polydiallyldimethylammonium chloride (20% by mass). After the addition is completed, no more glycerol is added. The other conditions are the same as in Example 1.

[0062] Performance testing:

[0063] 180° Peel Strength (GB / T 2792-2014): Samples were prepared and tested according to GB / T 2792-2014. Each sample was cut into strips with a width of 25 mm and a length of 200 mm and pasted onto three substrates: stainless steel plate, glass plate, and PET plate. The strips were rolled twice with a 2 kg roller at a speed of 300 mm / min, and then left to stand for 20 min at 23℃ and 50% relative humidity. A 180° peel test was performed using an electronic tensile testing machine at a speed of 300 mm / min. The peel force at the stable section was recorded and converted into peel strength (N / 25 mm). Each sample of each substrate was measured in parallel 5 times and the average value was taken.

[0064] Adhesion performance retention rate after high temperature and high humidity aging (GB / T 32368-2015): Each sample was aged according to GB / T 32368-2015: The sample attached to the stainless steel plate (sample preparation is the same as the 180° peel strength test) was placed in a constant temperature and humidity chamber and aged for 168 h at 70℃ and 90% relative humidity; after aging, it was taken out and restored for 2 h at 23℃ and 50% relative humidity, and the 180° peel strength was measured again according to GB / T 2792-2014; the retention rate (%) was calculated as the ratio of the value after aging to the value before aging. Each sample was measured in parallel 3 times and the average value was taken.

[0065] Rapid removal time after immersion in water, residual adhesive area ratio, and substrate damage evaluation (refer to GB / T 2792-2014 Sample Preparation and Peel Test): Cut each sample into 25mm×100mm labels and attach them to glass and PET plates. Roll them twice with a 2kg roller at a speed of 300mm / min, then let them stand for 24 hours at 23℃ and 50% relative humidity. Completely immerse the test plates in 25℃ deionized water for immersion times of 0.5min, 1min, 2min, 5min, and 10min. Remove the test plates at each immersion time point and remove them within 30s according to GB / T 2792-2014. 2792-2014 A 180° peel was performed at 300 mm / min, and the wet peel strength (N / 25 mm) was recorded. The immersion time corresponding to the first drop in wet peel strength to 0.5 N / 25 mm or below was defined as the rapid immersion removal time (min). After peeling, the substrate surface was rinsed with deionized water for 10 seconds and allowed to dry at 25℃ for 30 minutes. Photos were taken under the same lighting conditions and the images were binarized. The residual adhesive area ratio was calculated as (residual adhesive area / original label area) × 100% (%). At the same time, the substrate surface was observed with a 10x magnifying glass and graded as follows: "Grade 0: No visible damage; Grade 1: Slight fogging / scratches; Grade 2: Obvious fogging / scratches; Grade 3: Local peeling or obvious surface damage". The test results are recorded in Table 1.

[0066] Table 1 Performance Test Results

[0067] sample 180° peel strength (stainless steel, N / 25mm) 180° peel strength (glass, N / 25mm) 180° peel strength (PET, N / 25mm) Peel retention rate after aging (%) Rapid water immersion removal time (glass, min) Rapid water removal time (PET, min) Residual adhesive area ratio (glass, %) Residual adhesive area ratio (PET, %) Substrate damage grade (glass, grade) Basal damage grade (PET, grade) Example 1 17.8 18.6 13.4 89.6 2 5 0.9 1.4 0 0 Example 2 19.6 20.4 15.1 92.4 5 10 1.2 1.9 0 0 Example 3 17.1 18.0 13.0 88.1 1 2 0.4 0.7 0 0 Example 4 16.6 17.4 12.4 88.7 1 2 0.5 0.8 0 0 Example 5 15.3 16.2 11.6 84.9 5 10 1.3 2.1 0 0 Comparative Example 1 14.8 15.4 11.0 82.6 5 10 3.6 6.2 1 1 Comparative Example 2 14.2 15.0 10.6 80.9 5 10 4.1 6.8 1 2 Comparative Example 3 10.8 11.5 8.2 78.4 1 2 0.6 0.9 0 0 Comparative Example 4 17.0 12.8 9.5 83.8 2 5 1.8 2.9 0 1 Comparative Example 5 16.9 17.6 12.6 81.7 5 10 2.9 4.9 1 1 Comparative Example 6 15.9 16.7 12.0 74.3 2 5 3.2 5.6 1 2 Comparative Example 7 19.8 20.6 15.4 70.8 10 10 10.8 18.2 2 3 Comparative Example 8 16.1 16.9 12.1 79.3 5 10 3.4 5.9 1 2

[0068] Data Analysis:

[0069] As can be seen from the data in Table 1, the self-adhesive label paper prepared by the present invention exhibits high peel strength on both stainless steel and glass plates, and can also maintain a relatively stable adhesion level on polyethylene terephthalate plates. At the same time, it can still maintain a high adhesion retention rate after high temperature and high humidity aging, and can be quickly removed in a short time under water immersion conditions. After removal, the residual adhesive area ratio is low and the substrate damage level is no visible damage. The possible reasons are as follows: the combination of sodium chloroacetate carboxylation and itaconic acid aza-Michael addition introduces tunable carboxyl sites on branched polyethyleneimine, making it easier for the system charge to form a coatable electrostatic composite adhesive phase near the isoelectric point, which is beneficial for interfacial wetting and initial adhesion establishment in the dry state; the catechol functional groups introduced by dopamine hydrochloride grafting can enhance the multi-point effect on substrates such as glass and polyethylene terephthalate; the trivalent iron provided by ferric chloride hexahydrate forms more stable reversible coordination nodes after acidic pre-coordination and then increasing the pH, thereby improving the cohesiveness and aging resistance of the adhesive layer; the reversible network formed by polyvinyl alcohol and borate has both film-forming and swelling controllability under the competitive regulation of glycerol, which makes the adhesive layer maintain high adhesion in the dry state, while the ion pairs and reversible bonds are hydrated / shielded during hydration, making it easier to achieve controllable debonding at the interface and inhibit cohesive destruction, thereby reducing the risk of residual adhesive and substrate damage.

[0070] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 1 and 2, when branched polyethyleneimine undergoes only a single-path carboxyl group introduction (lacking itaconic acid azira-Michael addition or sodium chloroacetate carboxymethylation), the peel strength and aging retention rate decrease, and the immersion removal time is prolonged, accompanied by an increase in residual area ratio. The main reason for this may be that insufficient carboxyl group density and structural type lead to a narrower charge regulation window. The electrostatic composite morphology formed near the isoelectric point is more prone to hard flocculation or insufficient interfacial wetting, making it difficult to simultaneously achieve dry adhesion and wet hydration dissociation. This demonstrates the synergistic gain of dual-path carboxyl group introduction in charge regulation and interfacial adaptation.

[0071] As can be seen from the data in Table 1 for Example 1 and Comparative Example 3, when the pH during the electrostatic recombination stage is not adjusted to near the isoelectric point but is fixed under conditions deviating from the isoelectric point, the peel strength and aging retention rate of the samples decrease. While water immersion removal is easier to achieve, the overall adhesion reliability is insufficient. This may be because branched polyethyleneimine carries a stronger net charge when deviating from the isoelectric point, making it difficult to form a uniform coatable adhesive phase with polydiallyldimethylammonium chloride. Insufficient charge shielding and chain entanglement within the adhesive layer limit the establishment of initial dry adhesion. This result indicates that recombination near the isoelectric point is not a simple process parameter, but a key condition determining the coupling relationship between the adhesive phase morphology and performance.

[0072] As can be seen from the data in Example 1 and Comparative Example 4 in Table 1, the peel strength between the glass plate and the polyethylene terephthalate plate is significantly reduced when dopamine hydrochloride grafting is absent, accompanied by an increase in the risk of adhesive residue and damage. The main reason may be that the absence of catechol functional groups reduces the multi-point interaction and interfacial wetting ability of the adhesive layer on polar / weakly polar substrates. At the same time, the number of specific sites available for trivalent iron to form stable coordination nodes is reduced, making it easier to make an unfavorable trade-off between maintaining high adhesion and removability, resulting in either poor adhesion or easy adhesive residue. This conversely proves the dual contribution of catechol sites in interfacial interaction and reversible cohesive construction.

[0073] As can be seen from the data in Table 1 for Example 1 and Comparative Example 5, when sodium metabisulfite was not added during the dopamine hydrochloride grafting reaction, the aging retention rate decreased, the immersion removal time was prolonged, and the residual gum area ratio also increased. This may be because the lack of an antioxidant system makes catechols more susceptible to oxidative side reactions, weakening their reversible coordination ability and potentially introducing uneven interchain interactions. This results in a state where the internal structure of the gum layer exhibits both localized density and localized fragility. During immersion, this is not conducive to uniform hydration and dissociation, and also makes cohesive destruction more likely, thus manifesting as increased residual gum. This highlights the importance of an antioxidant system in "preserving reversible sites and avoiding uncontrollable side reactions."

[0074] As can be seen from the data in Table 1 for Example 1 and Comparative Example 6, when ferric chloride hexahydrate is added directly after increasing the pH without acidic pre-coordination, the aging retention rate is significantly reduced, accompanied by increased residue and damage level. The main reason may be that ferric chloride is more prone to hydrolysis in an alkaline environment, generating ineffective precipitates, resulting in insufficient and unevenly distributed effective coordination nodes, and decreased cohesion and shear resistance of the adhesive layer. During peeling and immersion, it tends to cause cohesive failure rather than controllable interfacial debonding, thus exhibiting the phenomenon of "unstable strength and easier residue." This indicates that the timing control and pre-coordination steps of ferric chloride introduction play a decisive role in performance coupling.

[0075] As can be seen from the data in Table 1 for Example 1 and Comparative Example 7, although the samples achieved high initial peel strength without the addition of borate, the rapid removal time after immersion in water was significantly prolonged, the residual adhesive area ratio and substrate damage level increased substantially, and the aging retention rate deteriorated significantly. This may be because the lack of a reversible network formed by polyvinyl alcohol and borate makes the adhesive layer more prone to a state of "high flow adhesion but insufficient cohesion" in the dry state, easily leading to stringing and cohesive breakage during peeling. Furthermore, the lack of controllable swelling channels and the lack of synergistic dissociation of reversible bonds during immersion in water makes it difficult for hydration to transform into interfacial deadhesion, ultimately resulting in high residual adhesive and high damage. This result demonstrates that "high adhesion" and "low residual removability" are not mutually exclusive indicators; the synergy of the reversible network and the coordination network is necessary to achieve a result greater than the sum of its parts.

[0076] As can be seen from the data in Example 1 and Comparative Example 8 in Table 1, when glycerol is added before electrostatic bonding and not replenished after bonding, the immersion removal time is prolonged, accompanied by an increase in residual adhesive and damage level, while the aging retention rate decreases. This may be because the competitive effect of glycerol on borates and polyvinyl alcohol, if occurring before the composite phase formation, alters the spatial partitioning and network construction path during the gel phase formation process. This results in the subsequently formed gel layer being more biased towards overall plasticization and localized density, weakening both dry-state cohesive stability and reducing uniform swelling and ion-pair hydrolysis dissociation efficiency during immersion. Therefore, the timing of glycerol addition is not a simple formulation adjustment, but rather a key factor determining whether the reversible network is both "enhanced and removable."

[0077] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high-adhesion self-adhesive label paper, characterized in that, The product includes a release liner, an adhesive layer disposed on the release liner, and a face material covering the adhesive layer; the adhesive layer is prepared from the following raw materials in parts by mass: 100 parts branched polyethyleneimine, 40-80 parts sodium chloroacetate, 20-60 parts itaconic acid, 3-5 parts dopamine hydrochloride, 0.2-0.45 parts ferric chloride hexahydrate, 90-110 parts 10% polyvinyl alcohol aqueous solution, 0.8-1.5 parts sodium tetraborate decahydrate, 8-15 parts sodium chloride, 40-60 parts 20% polydiallyl dimethyl ammonium chloride aqueous solution, and 8-15 parts glycerol; The branched polyethyleneimine is introduced into an iminodiacetic acid type carboxyl structural unit by sodium chloroacetate carboxylation, and then into an itaconic acid type dicarboxyl structural unit by itaconic acid aza-Michael addition, to obtain carboxylated branched polyethyleneimine.

2. The high-adhesion self-adhesive label paper according to claim 1, characterized in that, The isoelectric point of the carboxylated branched polyethyleneimine corresponds to a pH value of 7.2-8.6, wherein the pH value corresponding to the isoelectric point is the pH value when the absolute value of the zeta potential is ≤2mV as measured at 25°C.

3. The high-adhesion self-adhesive label paper according to claim 1, characterized in that, The carboxylated branched polyethyleneimine is grafted with dopamine at its carboxyl site to introduce a catechol functional group.

4. The high-adhesion self-adhesive label paper according to claim 1, characterized in that, The catechol functional group forms a coordination node with ferric iron.

5. The high-adhesion self-adhesive label paper according to claim 1, characterized in that, The polyvinyl alcohol and the sodium tetraborate decahydrate form a reversible network, and the glycerol competitively regulates the reversible network.

6. The high-adhesion self-adhesive label paper according to claim 1, characterized in that, The branched polyethyleneimine has a weight-average molecular weight of 20,000-30,000; the polydiallyldimethylammonium chloride has a weight-average molecular weight of 200,000-350,000; the polyvinyl alcohol has a weight-average molecular weight of 13,000-23,000 and a degree of alcoholysis of 87%-89%.

7. The high-adhesion self-adhesive label paper according to claim 1, characterized in that, The release liner is glassine silicone oil release liner with a basis weight of 60 g / m³. 2 The thickness is 54μm; the face material is a semi-gloss coated paper face material with a basis weight of 80g / m³. 2 .

8. The high-adhesion self-adhesive label paper according to claim 1, characterized in that, The wet coating amount of the adhesive layer is 45-55 g / m². 2 The material is dried at 30-35℃ for 10-12 hours to form a dry adhesive layer; the surface material and the dry adhesive layer are laminated by pressing them together three times under a pressure of 300kPa using a rubber roller.

9. A method for preparing high-adhesion self-adhesive label paper according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Using branched polyethyleneimine as raw material, a carboxylated branched polyethyleneimine solution was prepared by carboxylation with sodium chloroacetate and a azirmi-Michael addition reaction with itaconic acid; (2) Adjust the pH of the carboxylated branched polyethyleneimine solution to the pH value corresponding to the isoelectric point; (3) Under nitrogen protection and at pH 5-6, dopamine is grafted onto the carboxylated branched polyethyleneimine through a carbodiimine system to obtain a carboxylated branched polyethyleneimine solution containing catechol functional groups. (4) Adjust the solution obtained in step (3) to acidity and add ferric salt to form an acidic pre-coordination system, and then raise the pH to form a gel containing ferric coordination nodes; (5) Add polyvinyl alcohol aqueous solution, borate and sodium chloride to the adhesive solution obtained in step (4) in sequence, adjust the pH to the pH value corresponding to the isoelectric point, and then add polydiallyl dimethyl ammonium chloride aqueous solution for electrostatic composite. Then add glycerol and degas to obtain a coatable adhesive solution. (6) The coatable adhesive is applied to the release liner and dried to form a dry adhesive layer. Then the face material is laminated onto the dry adhesive layer and pressed together to obtain a high-adhesion self-adhesive label.