A PVA hydrogel tape and a preparation method thereof

Abstract

This invention discloses a PVA water-soluble adhesive tape and its preparation method, relating to the field of environmentally friendly polymer materials technology, and belonging to patent classification number C09J103 / 04. The method includes the following steps: mixing oxidized starch with deionized water, adding polyamide polyamine epichlorohydrin resin, and heating to carry out an ionic crosslinking reaction to obtain ionicly crosslinked starch; cooling the ionicly crosslinked starch, then adding carboxybetaine methacrylate and ammonium persulfate, and heating to carry out a free radical grafting reaction to obtain modified starch; adding polyvinyl alcohol aqueous solution and borax decahydrate to the modified starch to carry out a borate ester crosslinking reaction to obtain a water-soluble starch-based adhesive; preparing a PVA film substrate using a blown film process, uniformly coating the water-soluble starch-based adhesive onto the PVA film substrate using a precision coating machine, and then curling and slitting to obtain the PVA water-soluble adhesive tape. The PVA water-soluble adhesive tape prepared by this invention not only has good water solubility but also excellent adhesive properties.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly polymer materials technology, belonging to patent classification number C09J103 / 04, specifically to a PVA water-soluble tape and its preparation method. Background Technology

[0002] Water-soluble tapes, due to their environmentally friendly characteristics of completely dissolving under specific conditions and leaving no solid waste residue, have become important materials in packaging, medical, and temporary fixation of electronic components. Their structure mainly consists of two parts: a substrate and an adhesive. The substrate, acting as the tape's supporting framework, must simultaneously meet requirements for water solubility, mechanical strength, and film-forming stability. Currently, the most widely used substrate in the industry is polyvinyl alcohol (PVA) film, whose molecular chains are rich in hydroxyl groups. This allows it to dissolve rapidly in water and form a certain bonding force with the adhesive through intermolecular forces, ensuring the overall structural integrity of the tape. The adhesive is the core functional layer that enables effective adhesion between the tape and the adhered object. Its performance directly determines the tape's effectiveness. Furthermore, to ensure the overall water solubility of the tape, the adhesive must match the solubility characteristics of the substrate, i.e., possess good water solubility, to avoid environmental pollution or contamination of the adhered object due to adhesive residue.

[0003] In existing water-soluble tape preparation technologies, starch is the mainstream core natural material for adhesives, meeting both the requirements for water solubility and cost control. Starch molecules contain a large number of hydroxyl groups, a structural characteristic that naturally gives it good water solubility, matching the solubility of PVA substrates. Furthermore, starch is widely available and inexpensive, offering a significant cost advantage in industrial production. However, the core drawback of starch adhesives lies in their generally weak bonding performance, making it difficult to meet the reliability requirements of tape adhesion in practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a PVA water-soluble tape and its preparation method, so as to solve the technical problem of poor adhesive performance of starch in the adhesive component of the tape mentioned in the background art.

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

[0006] A method for preparing PVA water-soluble adhesive tape includes the following steps:

[0007] S1. Mix oxidized starch with deionized water, heat to gelatinize, cool down, add polyamide polyamine epichlorohydrin resin, adjust the pH to acidic with dilute sulfuric acid, heat to carry out ion crosslinking reaction, and obtain ion crosslinked starch.

[0008] S2. Cool the ion-crosslinked starch, then add carboxybetaine methacrylate and ammonium persulfate, and heat to carry out a free radical grafting reaction to obtain modified starch;

[0009] S3. Add polyvinyl alcohol aqueous solution and borax decahydrate to modified starch to carry out borate ester crosslinking reaction to obtain water-soluble starch-based adhesive.

[0010] S4. A PVA film substrate is prepared using a blown film process. A water-soluble starch-based adhesive is uniformly coated onto the PVA film substrate using a precision coating machine. After rolling and slitting, a PVA water-soluble tape is obtained.

[0011] In this invention, natural starch is used as the core adhesive component. First, by introducing polyamide polyamine epichlorohydrin resin, under acidic conditions, the cationic groups on its molecular chains undergo strong ionic bonding with the inherent anionic carboxyl groups on the oxidized starch molecular chains. This constructs a robust and reversible ionic cross-linking network between starch molecules. This three-dimensional network significantly enhances the bulk strength (cohesive force) of the adhesive, enabling the adhesive layer to effectively resist external stress without cohesive failure, fundamentally solving the problems of starch adhesive's brittleness and poor holding power. Second, through free radical graft copolymerization, the zwitterionic groups of carboxybenzene methacrylate are permanently introduced into the starch molecular chains. These zwitterionic groups have a strong hydration capacity, significantly reducing the surface energy of the adhesive. This allows it to spread and penetrate rapidly on the surface of the adhered material (especially low surface energy materials such as polyethylene and polypropylene) immediately after coating, achieving excellent instantaneous wetting. This not only greatly improves the initial tack (fast adhesion) of the tape, but its strong polarity also generates stronger ion-dipole interactions with the adhered surface, thereby significantly enhancing interfacial adhesion strength. Finally, by introducing borax decahydrate and polyvinyl alcohol, borate ions react with numerous ortho-cis-hydroxyl groups on the starch and polyvinyl alcohol molecular chains to form dynamically reversible borate ester bonds. These dynamic covalent bonds interpenetrate with the initially formed ionic crosslinking network, constituting a rigid-flexible interpenetrating polymer network. This structure provides extremely high cohesive strength and creep resistance at room temperature, further enhancing adhesion. Upon contact with hot water after disposal, the dynamic bonds reversibly break, the network disintegrates, and the tape dissolves rapidly, thus balancing high adhesion with water solubility, making it environmentally friendly. This invention achieves high adhesion strength between starch adhesives and the matrix, along with water solubility, through the aforementioned synergistic effect, making it both environmentally friendly and effective.

[0012] Preferably, in step S1, the method for preparing oxidized starch includes the following steps:

[0013] Cassava starch was dispersed in deionized water to prepare a starch slurry. The pH was adjusted to be alkaline, and then sodium hypochlorite was added. The mixture was heated and stirred to react. After filtration, drying, and pulverization, oxidized starch was obtained.

[0014] Preferably, in step S1, the mass ratio of oxidized starch to polyamide polyamine epichlorohydrin resin is 20:2-5.

[0015] Preferably, in step S1, the ionic crosslinking reaction temperature is 60-65°C and the crosslinking reaction time is 1-2 hours.

[0016] Preferably, in step S2, the ion-crosslinked starch is cooled to 40-45°C.

[0017] Preferably, in step S2, after the ionicly cross-linked starch is cooled, the subsequent reaction steps are as follows:

[0018] Hydroxypropyl-β-cyclodextrin was added to the reaction system and stirred to disperse it fully. Then, a mixed solution of carboxybetaine methacrylate and adamantane methylamine was added and the reaction was kept at a constant temperature. Finally, ammonium persulfate was added to carry out a free radical grafting reaction to obtain modified starch.

[0019] In the technical solution of this invention, the research team found in experiments that although carboxybetaine methacrylate monomer has strong hydrophilicity, it lacks sufficiently strong specific intermolecular forces with the already formed positively charged polyamide polyamine epichlorohydrin resin-starch ion network. This results in the uneven distribution of carboxybetaine methacrylate molecules in the system after simple mechanical stirring and mixing, which cannot effectively combine with the network, thereby affecting the effect of carboxybetaine methacrylate monomer on improving the adhesive bonding performance. To further address this technical problem, this invention utilizes the ammonolysis reaction between the amino group of adamantane methylamine and the ester bond of carboxybetaine methacrylate to covalently attach the hydrophobic adamantyl group to the hydrophilic carboxybetaine methacrylate molecule, synthesizing a carboxybetaine methacrylate-adamantane derivative. Furthermore, leveraging the molecular structure of hydroxypropyl-β-cyclodextrin, whose hydrophilic outer wall exhibits good compatibility with aqueous systems, and whose hydrophobic inner cavity can precisely encapsulate the terminal adamantyl group of the carboxybetaine methacrylate-adamantane derivative, forming a stable host-guest inclusion complex, this super-resolution... The effect of this component is equivalent to using hydroxypropyl-β-cyclodextrin as a uniformly dispersed anchor point, which orients and uniformly fixes and arranges carboxybetaine methacrylate molecules around the polyamide polyamine epichlorohydrin resin-starch network. This solves the problem of uneven distribution of carboxybetaine methacrylate and creates ideal conditions for its subsequent efficient and uniform free radical graft copolymerization with starch molecular chains. Ultimately, it ensures the uniform distribution of zwitterionic groups in the three-dimensional network and maximizes the effect of carboxybetaine methacrylate on improving the adhesive properties of starch adhesives.

[0020] Preferably, the mass ratio of carboxybetaine methacrylate to adamantane methylamine is 8:1 to 4.

[0021] Preferably, the heat preservation reaction temperature is 40°C and the reaction time is 30 min.

[0022] Preferably, in step S3, the borate ester crosslinking reaction temperature is 50–60°C and the reaction time is 1–3 h.

[0023] A PVA water-soluble adhesive tape is prepared by the method described in the preceding claims.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. By forming an ionic crosslinking network between polyamide polyamine epichlorohydrin resin and oxidized starch under acidic conditions, the bulk strength of the adhesive is enhanced, solving the problems of high brittleness and poor holding power of starch adhesives. Then, by introducing the zwitterionic groups of carboxybenzene methacrylate into the starch molecular chain through free radical grafting, the surface energy of the adhesive is reduced, improving initial tack and interfacial adhesion strength. Finally, by forming dynamic and reversible borate ester bonds with decahydrate borax, polyvinyl alcohol, and starch, a rigid-flexible interpenetrating polymer network is constructed, further improving holding power and creep resistance. The synergistic effect of the three results in high bonding strength.

[0026] 2. By utilizing the ammonolysis reaction between the amino group of adamantane methylamine and the ester bond of carboxybetaine methacrylate, the hydrophobic adamantane group is covalently linked to the hydrophilic carboxybetaine methacrylate molecule, synthesizing a carboxybetaine methacrylate-adamantane derivative. Then, taking advantage of the molecular structure of hydroxypropyl-β-cyclodextrin, its hydrophilic outer wall exhibits good compatibility with aqueous systems, while its hydrophobic inner cavity can precisely encapsulate the terminal adamantane group of the carboxybetaine methacrylate-adamantane derivative, forming a stable host-guest inclusion complex. This supramolecular interaction is equivalent to... Hydroxypropyl-β-cyclodextrin acts as a uniformly dispersed anchoring point, orienting and uniformly fixing carboxybetaine methacrylate molecules around the polyamide polyamine epichlorohydrin resin-starch network. This solves the problem of uneven distribution of carboxybetaine methacrylate, creating ideal conditions for its subsequent efficient and uniform free radical graft copolymerization with starch molecular chains. Ultimately, it ensures the uniform distribution of zwitterionic groups in the three-dimensional network, maximizing the effect of carboxybetaine methacrylate on improving the adhesive properties of starch adhesives. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] Preparation of oxidized starch:

[0030] 1000g of cassava starch was dispersed in 1500mL of deionized water to obtain a starch slurry. This slurry was transferred to a reaction vessel, and mechanical stirring was started while the temperature was raised to 35℃. The pH of the system was adjusted to 9.0-9.5 using 3% sodium hydroxide solution. Then, 100mL of sodium hypochlorite solution with an effective chlorine content of 6% was slowly added dropwise, controlling the dropping rate to be completed within 30 minutes. During this period, the pH of the reaction system was continuously monitored and maintained within the range of 9.0-10.0. After the addition was complete, the reaction was continued at 45℃ for 3 hours. After the reaction was completed, the pH of the system was neutralized to 6.5-7.0 using 10% dilute sulfuric acid. The reaction product was filtered and repeatedly washed with deionized water until no chloride ions were detected. Finally, the filter cake was dried in a vacuum oven at 50℃ to constant weight, pulverized, and passed through a 100-mesh sieve to obtain oxidized starch.

[0031] Preparation of PVA hydrosol tape:

[0032] Step 1: Add 500g of oxidized starch and 1250mL of deionized water to a four-necked flask, turn on mechanical stirring (200rpm), heat in a water bath to 90℃ and maintain for 30min to allow the starch to gelatinize fully. Then cool the system to 60℃, slowly add an aqueous solution of polyamide polyamine epichlorohydrin resin (100g of polyamide polyamine epichlorohydrin resin dissolved in 600mL of deionized water), and continue stirring to mix thoroughly. Slowly adjust the pH of the system to 5.0 with 10% dilute sulfuric acid, and maintain the temperature at 63℃ for 1.5h. After the reaction is complete, a milky white, ionically cross-linked starch with significantly increased viscosity is obtained.

[0033] Step 2: Cool the ionically cross-linked starch to 43℃, add 20g of hydroxypropyl-β-cyclodextrin, and stir for 30min to ensure thorough dispersion. Separately, mix 80g of carboxybetaine methacrylate and 30g of adamantane methylamine to prepare a mixed solution, and slowly add it dropwise to the reaction system while stirring. After the addition is complete, maintain the temperature at 40℃ for 30min. Then add 5g of ammonium persulfate, stir to dissolve, and carry out a free radical grafting reaction at 40℃ for 2h. During the reaction, the viscosity of the system gradually increases, resulting in modified starch with improved flowability.

[0034] Step 3: Maintain the system temperature at 55℃, add 1000mL of 10wt% polyvinyl alcohol aqueous solution (degree of hydrolysis 88%, degree of polymerization 500), and stir for 30min to ensure thorough mixing. Then add 20g of borax decahydrate and continue the reaction for 2.5h. During this period, the viscosity of the system further increases, forming a uniform paste-like colloid, thus obtaining a water-soluble starch-based adhesive with good coating rheological properties.

[0035] Step 4: Mix 1000g of polyvinyl alcohol resin (99% degree of hydrolysis, 1700 degree of polymerization), 150g of plasticizer glycerin, 10g of lubricant stearic acid, and 5g of antioxidant 1010 evenly. Then, melt-extrude and granulate the mixture using a twin-screw extruder (five temperature zones: 175℃ / 195℃ / 210℃ / 205℃ / 200℃). Next, blow-mold the mixture using a single-screw blow molding machine (feeding section 185℃, middle section 200℃, front section 215℃) to obtain a PVA film with a thickness of 0.05mm. Apply the water-soluble starch-based adhesive prepared above evenly to the PVA film substrate using a precision coating machine (coating amount 60g / m²). 2 The PVA water-soluble adhesive tape is dried in an oven at 60℃ for 1 minute, and then rolled and cut to obtain the tape.

[0036] Example 2

[0037] The preparation of oxidized starch was the same as in Example 1.

[0038] Preparation of PVA hydrosol tape:

[0039] Step 1: Add 500g of oxidized starch and 1250mL of deionized water to a four-necked flask, turn on mechanical stirring (200rpm), and heat in a water bath to 90℃ and maintain for 30min to allow the starch to gelatinize fully. Then cool the system to 60℃, and slowly add an aqueous solution of polyamide polyamine epichlorohydrin resin (70g of polyamide polyamine epichlorohydrin resin dissolved in 600mL of deionized water), stirring continuously until homogeneous. Slowly adjust the pH of the system to 5.0 with 10% dilute sulfuric acid, and maintain the temperature at 63℃ for 1.5h. After the reaction is complete, a milky white, ionically cross-linked starch with significantly increased viscosity is obtained.

[0040] Step 2: Cool the ionically cross-linked starch to 43℃, add 20g of hydroxypropyl-β-cyclodextrin, and stir for 30min to ensure thorough dispersion. Separately, mix 80g of carboxybetaine methacrylate and 20g of adamantane methylamine to prepare a mixed solution. Slowly add this solution dropwise to the reaction system while stirring. After the addition is complete, maintain the temperature at 40℃ for 30min. Then add 5g of ammonium persulfate, stir to dissolve, and carry out a free radical grafting reaction at 40℃ for 2h. During the reaction, the viscosity of the system gradually increases, resulting in modified starch with improved flowability.

[0041] Step 3: Maintain the system temperature at 55℃, add 1000mL of 10wt% polyvinyl alcohol aqueous solution (degree of hydrolysis 88%, degree of polymerization 500), and stir for 30min to ensure thorough mixing. Then add 20g of borax decahydrate and continue the reaction for 1.5h. During this period, the viscosity of the system further increases, forming a uniform paste-like colloid, thus obtaining a water-soluble starch-based adhesive with good coating rheological properties.

[0042] Step 4: Mix 1000g of polyvinyl alcohol resin (99% degree of hydrolysis, 1700 degree of polymerization), 150g of plasticizer glycerin, 10g of lubricant stearic acid, and 5g of antioxidant 1010 evenly. Then, melt-extrude and granulate the mixture using a twin-screw extruder (five temperature zones: 175℃ / 195℃ / 210℃ / 205℃ / 200℃). Next, blow-mold the mixture using a single-screw blow molding machine (feeding section 185℃, middle section 200℃, front section 215℃) to obtain a PVA film with a thickness of 0.05mm. Apply the water-soluble starch-based adhesive prepared above evenly to the PVA film substrate using a precision coating machine (coating amount 60g / m²). 2 The PVA water-soluble adhesive tape is dried in an oven at 60℃ for 1 minute, and then rolled and cut to obtain the tape.

[0043] Example 3

[0044] The preparation of oxidized starch was the same as in Example 1.

[0045] Preparation of PVA hydrosol tape:

[0046] Step 1: Add 500g of oxidized starch and 1250mL of deionized water to a four-necked flask, turn on mechanical stirring (200rpm), heat in a water bath to 90℃ and maintain for 30min to allow the starch to gelatinize fully. Then cool the system to 60℃, slowly add an aqueous solution of polyamide polyamine epichlorohydrin resin (90g of polyamide polyamine epichlorohydrin resin dissolved in 600mL of deionized water), and continue stirring to mix thoroughly. Slowly adjust the pH of the system to 5.0 with 10% dilute sulfuric acid, and maintain the temperature at 63℃ for 1.5h. After the reaction is complete, a milky white, ionically cross-linked starch with significantly increased viscosity is obtained.

[0047] Step 2: Cool the ionically cross-linked starch to 43℃, add 20g of hydroxypropyl-β-cyclodextrin, and stir for 30min to ensure thorough dispersion. Separately, mix 80g of carboxybetaine methacrylate and 25g of adamantane methylamine to prepare a mixed solution, and slowly add it dropwise to the reaction system while stirring. After the addition is complete, maintain the temperature at 40℃ for 30min. Then add 5g of ammonium persulfate, stir to dissolve, and carry out a free radical grafting reaction at 40℃ for 2h. During the reaction, the viscosity of the system gradually increases, resulting in modified starch with improved flowability.

[0048] Step 3: Maintain the system temperature at 55℃, add 1000mL of 10wt% polyvinyl alcohol aqueous solution (degree of hydrolysis 88%, degree of polymerization 500), and stir for 30min to ensure thorough mixing. Then add 20g of borax decahydrate and continue the reaction for 2h. During this period, the viscosity of the system further increases, forming a uniform paste-like colloid, thus obtaining a water-soluble starch-based adhesive with good coating rheological properties.

[0049] Step 4: Mix 1000g of polyvinyl alcohol resin (99% degree of hydrolysis, 1700 degree of polymerization), 150g of plasticizer glycerin, 10g of lubricant stearic acid, and 5g of antioxidant 1010 evenly. Then, melt-extrude and granulate the mixture using a twin-screw extruder (five temperature zones: 175℃ / 195℃ / 210℃ / 205℃ / 200℃). Next, blow-mold the mixture using a single-screw blow molding machine (feeding section 185℃, middle section 200℃, front section 215℃) to obtain a PVA film with a thickness of 0.05mm. Apply the water-soluble starch-based adhesive prepared above evenly to the PVA film substrate using a precision coating machine (coating amount 60g / m²). 2 The PVA water-soluble adhesive tape is dried in an oven at 60℃ for 1 minute, and then rolled and cut to obtain the tape.

[0050] Example 4

[0051] The preparation of oxidized starch was the same as in Example 1.

[0052] Preparation of PVA hydrosol tape:

[0053] Step 1: Add 500g of oxidized starch and 1250mL of deionized water to a four-necked flask, turn on mechanical stirring (200rpm), heat in a water bath to 90℃ and maintain for 30min to allow the starch to gelatinize fully. Then cool the system to 60℃, slowly add an aqueous solution of polyamide polyamine epichlorohydrin resin (125g of polyamide polyamine epichlorohydrin resin dissolved in 600mL of deionized water), and continue stirring to mix thoroughly. Slowly adjust the pH of the system to 5.0 with 10% dilute sulfuric acid, and maintain the temperature at 65℃ for 2h. After the reaction is complete, a milky white, ionically cross-linked starch with significantly increased viscosity is obtained.

[0054] Step 2: Cool the ionically cross-linked starch to 45℃, add 20g of hydroxypropyl-β-cyclodextrin, and stir for 30min to ensure thorough dispersion. Separately, mix 80g of carboxybetaine methacrylate and 40g of adamantane methylamine to prepare a mixed solution, and slowly add it dropwise to the reaction system while stirring. After the addition is complete, maintain the reaction temperature at 40℃ for 30min. Then add 5g of ammonium persulfate, stir to dissolve, and carry out a free radical grafting reaction at 40℃ for 2h. During the reaction, the viscosity of the system gradually increases, resulting in modified starch with improved flowability.

[0055] Step 3: Maintain the system temperature at 60℃, add 1000mL of 10wt% polyvinyl alcohol aqueous solution (degree of hydrolysis 88%, degree of polymerization 500), and stir for 30min to ensure thorough mixing. Then add 20g of borax decahydrate and continue the reaction for 3h. During this period, the viscosity of the system further increases, forming a uniform paste-like colloid, thus obtaining a water-soluble starch-based adhesive with good coating rheological properties.

[0056] Step 4: Mix 1000g of polyvinyl alcohol resin (99% degree of hydrolysis, 1700 degree of polymerization), 150g of plasticizer glycerin, 10g of lubricant stearic acid, and 5g of antioxidant 1010 evenly. Then, melt-extrude and granulate the mixture using a twin-screw extruder (five temperature zones: 175℃ / 195℃ / 210℃ / 205℃ / 200℃). Next, blow-mold the mixture using a single-screw blow molding machine (feeding section 185℃, middle section 200℃, front section 215℃) to obtain a PVA film with a thickness of 0.05mm. Apply the water-soluble starch-based adhesive prepared above evenly to the PVA film substrate using a precision coating machine (coating amount 60g / m²). 2 The PVA water-soluble adhesive tape is dried in an oven at 60℃ for 1 minute, and then rolled and cut to obtain the tape.

[0057] Example 5

[0058] The preparation of oxidized starch was the same as in Example 1.

[0059] Preparation of PVA hydrosol tape:

[0060] Step 1: Add 500g of oxidized starch and 1250mL of deionized water to a four-necked flask, turn on mechanical stirring (200rpm), heat in a water bath to 90℃ and maintain for 30min to allow the starch to gelatinize fully. Then cool the system to 60℃, slowly add an aqueous solution of polyamide polyamine epichlorohydrin resin (50g of polyamide polyamine epichlorohydrin resin dissolved in 600mL of deionized water), and continue stirring to mix thoroughly. Slowly adjust the pH of the system to 5.0 with 10% dilute sulfuric acid, and maintain the temperature at 60℃ for 1h. After the reaction is complete, a milky white, ionically cross-linked starch with significantly increased viscosity is obtained.

[0061] Step 2: Cool the ionically cross-linked starch to 40℃, add 20g of hydroxypropyl-β-cyclodextrin, and stir for 30min to ensure thorough dispersion. Separately, mix 80g of carboxybetaine methacrylate and 10g of adamantane methylamine to prepare a mixed solution, and slowly add it dropwise to the reaction system while stirring. After the addition is complete, maintain the reaction temperature at 40℃ for 30min. Then add 5g of ammonium persulfate, stir to dissolve, and carry out a free radical grafting reaction at 40℃ for 2h. During the reaction, the viscosity of the system gradually increases, resulting in modified starch with improved flowability.

[0062] Step 3: Maintain the system temperature at 50℃, add 1000mL of 10wt% polyvinyl alcohol aqueous solution (degree of hydrolysis 88%, degree of polymerization 500), and stir for 30min to ensure thorough mixing. Then add 20g of borax decahydrate and continue the reaction for 1h. During this period, the viscosity of the system further increases, forming a uniform paste-like colloid, thus obtaining a water-soluble starch-based adhesive with good coating rheological properties.

[0063] Step 4: Mix 1000g of polyvinyl alcohol resin (99% degree of hydrolysis, 1700 degree of polymerization), 150g of plasticizer glycerin, 10g of lubricant stearic acid, and 5g of antioxidant 1010 evenly. Then, melt-extrude and granulate the mixture using a twin-screw extruder (five temperature zones: 175℃ / 195℃ / 210℃ / 205℃ / 200℃). Next, blow-mold the mixture using a single-screw blow molding machine (feeding section 185℃, middle section 200℃, front section 215℃) to obtain a PVA film with a thickness of 0.05mm. Apply the water-soluble starch-based adhesive prepared above evenly to the PVA film substrate using a precision coating machine (coating amount 60g / m²). 2 The PVA water-soluble adhesive tape is dried in an oven at 60℃ for 1 minute, and then rolled and cut to obtain the tape.

[0064] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the water-soluble starch-based adhesive used in step 4 is replaced with ordinary starch as the adhesive.

[0065] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that steps 2 and 3 are omitted, and the water-soluble starch-based adhesive used in step 4 is replaced with the ion-crosslinked starch obtained in step 1.

[0066] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that step 3 is omitted, and the water-soluble starch-based adhesive used in step 4 is replaced with the modified starch obtained in step 2.

[0067] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that hydroxypropyl-β-cyclodextrin is not added in step 2.

[0068] Performance testing:

[0069] 1. Initial Tack Test: Referring to GB / T 4852-2002 "Test Method for Initial Tack of Pressure-Sensitive Adhesive Tapes (Rolling Ball Method)", the test sample was cut into 25mm × 100mm pieces. The stainless steel test plate was cleaned with anhydrous ethanol (surface roughness Ra ≤ 0.8μm). After the ethanol had completely evaporated, the piece was flatly pasted onto the center of the stainless steel plate, ensuring no air bubbles or wrinkles. A 2kg standard roller was used to roll back and forth on the piece twice at a speed of 300mm / min, and the plate was left to stand for 5 minutes. The stainless steel plate was tilted at 30°. The smallest steel ball from No. 1 (diameter 1.59mm) to No. 12 (diameter 12.70mm) was selected and rolled freely down the guide rail from 100mm above the top of the steel plate. The largest steel ball number that remained on the adhesive surface of the piece for more than 5 seconds was recorded. Each group of samples was tested three times, and the average value was taken as the initial tack result. The test results are shown in Table 1.

[0070] 2. Holding Power Test: Referring to GB / T 4851-2014 "Test Method for Holding Power of Pressure-Sensitive Adhesive Tapes", the test sample was cut into 25mm×125mm pieces. After cleaning the stainless steel test plate (Ra≤0.8μm), one end of the 25mm×25mm area of ​​the piece was pasted onto the steel plate. A 2kg standard roller was used to roll the piece back and forth twice at a speed of 300mm / min, followed by a 20min resting period. The steel plate was then vertically fixed on the test frame, and a 1kg standard weight (including the hook) was suspended from the free end of the piece. The ambient temperature was (23±2)℃, and the relative humidity was (50±5)%. The time it took for the piece to completely peel off from the steel plate was recorded. If it did not peel off within 100h, it was recorded as "≥100h". Each group of samples was tested three times, and the average value was taken as the holding power result. The test results are shown in Table 1.

[0071] 3. Peel Strength Test: Referring to GB / T 2792-2014 "Test Method for 180° Peel Strength of Pressure-Sensitive Adhesive Tapes", the test sample was cut into 25mm × 200mm pieces. The substrate was a 0.1mm thick polypropylene (PP) film. After cleaning the substrate surface with anhydrous ethanol, the sample was flatly pasted onto the substrate and rolled back and forth three times at a speed of 300mm / min using a 2kg standard roller. The sample was then left to stand for 24 hours. The pasted sample was then fixed on a tensile testing machine, with a tensile speed of 300mm / min. A peel test was performed at 180°, recording the force changes during the peeling process. The average force value at the stable point was taken as the 180° peel strength (unit: N / 25mm). Each group of samples was tested five times, and outliers were removed before taking the average value. The test results are shown in Table 1.

[0072] 4. Water solubility test: Cut the test sample into 50mm×50mm pieces and accurately weigh them (recorded as m0). Pour 500mL of deionized water into a 1000mL beaker, heat to (80±2)℃ and maintain the temperature, and place a stir bar (300rpm). Completely immerse the sample piece in the hot water, start timing, and observe the dissolution state of the sample piece. When there is no obvious solid residue in the solution and no residue remains on the filter screen after filtration through a 100-mesh screen, stop timing and record the dissolution time; if it is not completely dissolved within 30 minutes, record it as ">30min". Each group of samples is tested 3 times, and the average value is taken as the dissolution time result. The test results are shown in Table 1.

[0073] Table 1:

[0074]

[0075] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing PVA hydrosol tape, characterized in that, Includes the following steps: S1. Cassava starch is dispersed in deionized water to prepare starch slurry, the pH is adjusted to alkaline, sodium hypochlorite is added, the mixture is heated and stirred to react, and after filtration, drying and pulverization, oxidized starch is obtained. Oxidized starch was mixed with deionized water, heated to gelatinize, cooled, and polyamide polyamine epichlorohydrin resin was added. The pH was adjusted to acidic with dilute sulfuric acid, and the mixture was heated to carry out an ionic crosslinking reaction to obtain ionic crosslinked starch. S2. Cool the ion-crosslinked starch to 40-45℃, add hydroxypropyl-β-cyclodextrin to the reaction system, stir to disperse it fully, then add a mixed solution of carboxybetaine methacrylate and adamantane methylamine, keep the reaction at the temperature, then add ammonium persulfate to carry out free radical grafting reaction to obtain modified starch. S3. Add polyvinyl alcohol aqueous solution and borax decahydrate to modified starch to carry out borate ester crosslinking reaction to obtain water-soluble starch-based adhesive. S4. A PVA film substrate is prepared using a blown film process. A water-soluble starch-based adhesive is uniformly coated onto the PVA film substrate using a precision coating machine. After rolling and slitting, a PVA water-soluble tape is obtained.

2. The method for preparing a PVA hydrosol tape according to claim 1, characterized in that, In step S1, the mass ratio of oxidized starch to polyamide polyamine epichlorohydrin resin is 20:2-5.

3. The method for preparing a PVA hydrosol tape according to claim 1, characterized in that, In step S1, the ionic crosslinking reaction temperature is 60-65℃ and the crosslinking reaction time is 1-2h.

4. The method for preparing a PVA hydrosol tape according to claim 1, characterized in that, In step S2, the mass ratio of carboxybetaine methacrylate to adamantane methylamine is 8:1 to 4.

5. The method for preparing a PVA hydrosol tape according to claim 1, characterized in that, In step S2, the heat preservation reaction temperature is 40°C and the reaction time is 30 min.

6. The method for preparing a PVA hydrosol tape according to claim 1, characterized in that, In step S3, the borate ester crosslinking reaction temperature is 50-60℃ and the reaction time is 1-3h.

7. A PVA water-soluble adhesive tape, characterized in that, It is prepared by the method described in any one of claims 1-6.

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