A PVA adhesive tape and its preparation method
By activating plant gum with endo-β-glucanase to form a graft copolymer with PVA, and combining it with thickener and sepiolite dispersion, the problem of unstable bonding performance of PVA adhesive strips during humidity changes was solved, and the bonding performance stability under different humidity environments was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG SENGONG NEW MATERIAL TECH CO LTD
- Filing Date
- 2025-08-25
- Publication Date
- 2026-05-22
AI Technical Summary
The bonding performance of PVA adhesive strips is unstable during humidity changes, leading to bonding failure.
Plant gum is activated by endo-β-glucanase and grafted with PVA through an ultrasound-assisted enzymatic hydrolysis reaction to form a graft copolymer. Combined with thickener and sepiolite dispersion, an interpenetrating network structure is formed to enhance the adhesive's humidity adaptability.
Maintain stable bonding performance under different humidity environments, prevent adhesive failure due to humidity changes, and maintain good bonding strength.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of packaging materials technology. More specifically, it relates to a PVA adhesive strip and its preparation method. Background Technology
[0002] PVA adhesive strips are increasingly replacing traditional adhesives in packaging, medical, and electronics industries due to their biodegradability, cost advantages, and formulation flexibility.
[0003] Currently, commonly used PVA adhesive strip systems use basic formulations such as PVA with glycerin as a plasticizer, but they require the addition of crosslinking agents, such as borax, to improve water resistance.
[0004] As environmental protection requirements have become more stringent, environmentally friendly adhesives based on PVA-plant adhesives have emerged. These adhesives have good environmental safety and excellent water solubility. However, the inventors discovered that the adhesive stability of these adhesives begins to decline when humidity fluctuates, leading to adhesive failure.
[0005] Therefore, improving the stability of product properties during humidity changes is one of the technical challenges that needs to be overcome. Summary of the Invention
[0006] The technical problem this invention aims to solve is the issue that, during actual use, the bonding performance of PVA adhesive strips fluctuates significantly with changes in ambient humidity, leading to bonding failure. To address this challenge, this invention provides a PVA adhesive strip and its preparation method.
[0007] The purpose of this invention is to provide a PVA adhesive strip.
[0008] Another object of the present invention is to provide a method for preparing PVA adhesive strips.
[0009] The above-mentioned objective of this invention is achieved through the following technical solution:
[0010] A method for preparing a PVA adhesive strip, comprising the following specific steps:
[0011] Plant gum activation:
[0012] Guar gum and water are mixed and swollen at a mass ratio of 1:15-20. Then, 0.3-0.5% of endo-β-glucanase by mass of guar gum is added. The mixture is subjected to sonication at pH 5.0-5.2, temperature 48-52℃, and ultrasonic frequency 50-60kHz for 30-45 minutes. The enzyme is then inactivated by heating and cooled to obtain activated plant gum solution.
[0013] Raw material preparation:
[0014] By weight, take 100-120 parts of PVA solution with a mass fraction of 20-25%, 120-130 parts of activated plant gum solution, 60-70 parts of thickener solution with a mass fraction of 8-10%, 8-12 parts of composite modifier, and 0.6-0.8 parts of potassium persulfate.
[0015] The composite modifier is composed of glycerol and triethyl citrate in a mass ratio of 1.5-1.8:1.
[0016] Low-temperature complex reaction:
[0017] After stirring and mixing the PVA solution and activated plant gum solution evenly, add the thickener solution, continue stirring and mixing evenly, add the composite modifier and potassium persulfate, keep the mixture at 40-45℃ for 2-4 hours, then age it for 24-36 hours, and then discharge the mixture to obtain the mixed gum solution.
[0018] After the mixed adhesive solution is applied and dried, the PVA adhesive strip is obtained.
[0019] The beneficial effects of the above technical solution are as follows:
[0020] The above technical solution uses an endoglucanase to selectively cleave the β-1,4 glycosidic bonds in plant gums, degrading long-chain polysaccharides into fragments with molecular weights of 50,000 to 100,000. This exposes more hydroxyl (-OH) active sites, improving the subsequent grafting efficiency with PVA. At the same time, it reduces the pseudoplasticity of the solution, making the viscosity easier to control during the reaction and avoiding instability in the reaction results due to viscosity instability during the reaction.
[0021] In the enzymatic hydrolysis process, ultrasound assistance is further employed to utilize the cavitation effect of ultrasound to disrupt the microcrystalline structure of plant gums and promote the stretching of their molecular chains, thereby synergizing with the enzymatic hydrolysis process and enabling the hydrolysis products to form a uniform colloid.
[0022] During the initiation reaction stage, potassium persulfate can decompose at low temperatures to generate free radicals. These free radicals preferentially attack the secondary hydroxyl sites on the PVA molecular chain, forming PVA macromolecular free radicals. The reduced terminal aldehyde groups (-CHO) of the plant gum after chain scission undergo nucleophilic addition with the PVA free radicals, forming a PVA-plant gum graft copolymer. This allows the grafted chains and free plant gum molecules to form a three-dimensional network through hydrogen bonds. Under the action of this three-dimensional network, hydrogen bonds are enhanced at low humidity (increasing cohesion), and some hydrogen bonds dissociate and release stress at high humidity (preventing cracking). While ensuring the water solubility and biodegradability of the adhesive, its bonding stability under different humidity environments is improved.
[0023] Furthermore, the thickener solution is selected from any one of the following: sodium carboxymethyl cellulose solution, hydroxyethyl cellulose solution, carboxymethyl hydroxyethyl cellulose solution, and carboxymethyl hydroxypropyl cellulose solution;
[0024] Furthermore, the preparation method for the thickener solution includes:
[0025] After mixing the thickener and water in the specified mass ratio, allow them to stand and swell for 60-80 minutes at a temperature of 25-30℃, and then stir at a low speed of 80-120 r / min for 30-45 minutes.
[0026] Furthermore, the thickener solution is a sodium carboxymethyl cellulose solution, wherein the degree of substitution of the sodium carboxymethyl cellulose is 0.8-0.9.
[0027] The beneficial effects of the above technical solution are as follows:
[0028] With a degree of substitution of 0.8-0.9, meaning that 8-9 hydroxyl groups out of every 10 glucose units are replaced by carboxymethyl groups, this falls into the medium-to-high degree of substitution category. In this type of sodium carboxymethyl cellulose product, the electrostatic repulsion of the carboxymethyl groups is sufficient to overcome the hydrogen bonds between cellulose molecular chains, allowing them to fully extend; however, the remaining unsubstituted hydroxyl groups (10-20%) still maintain the rigidity of the molecular chains, preventing excessive deentanglement; the hydroxyl groups of PVA form directional hydrogen bonds with the unsubstituted hydroxyl groups of CMC, while the carboxymethyl groups prevent excessive crystallization of PVA through electrostatic repulsion; thus, PVA and sodium carboxymethyl cellulose form an interpenetrating network, enabling the product to buffer changes in environmental humidity without softening the gel layer due to excessive swelling.
[0029] Furthermore, the low-temperature composite reaction also includes:
[0030] The PVA solution and activated plant gum solution were kept at 50-55℃ and stirred at 180-220r / min for 30-40min.
[0031] Add the thickener solution and continue to react for 20-30 minutes at a temperature of 42-45℃ and a stirring speed of 220-250 r / min.
[0032] Subsequently, a composite modifier and potassium persulfate were added, and the mixture was kept at 40-45℃ and stirred at 200-220 r / min for 2-4 hours. After cooling to 25℃, it was kept at 25℃ and aged for 24-36 hours before being discharged to obtain a mixed adhesive solution.
[0033] Furthermore, the low-temperature composite reaction also includes:
[0034] After mixing PVA solution, activated plant gum solution, and sepiolite dispersion (20-25% by mass of PVA solution), the mixture is kept at 50-55℃ and stirred at 180-220 r / min for 30-40 min.
[0035] The sepiolite dispersion is obtained by ultrasonic dispersion of sepiolite and water mixed at a mass ratio of 1:8-10.
[0036] The beneficial effects of the above technical solution are as follows:
[0037] By further introducing sepiolite into the system, if the ambient humidity is too high, sepiolite can preferentially capture free water molecules and alleviate the swelling of PVA; while when the ambient humidity is too low, it can slowly release the stored moisture, delay the embrittlement and cracking of the adhesive layer, so that the bonding performance of the product remains relatively stable when the humidity environment changes.
[0038] In addition, the inventors discovered that magnesium ions in sepiolite can form coordination bonds with PVA-plant adhesive graft copolymers. These coordination bonds can reversibly dissociate / recombine within a certain humidity range, achieving humidity self-adaptation and thus keeping the product's bonding performance stable.
[0039] Furthermore, the sepiolite dispersion also includes 20-25% fumed silica by weight of sepiolite.
[0040] Furthermore, the PVA is polyvinyl alcohol with a degree of hydrolysis of 87-89%, and the average degree of polymerization of the polyvinyl alcohol is 2500-2600, and the weight-average molecular weight is 120000-128000.
[0041] A PVA adhesive strip is prepared by the above-described preparation method. Detailed Implementation
[0042] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.
[0043] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.
[0044] Example 1
[0045] Preparation of thickener solution:
[0046] After mixing the thickener and water in a certain mass ratio, the mixture was allowed to stand and swell for 60 minutes at a temperature of 25°C. Then, it was stirred at a low speed of 80 r / min for 30 minutes to obtain a thickener solution with a mass fraction of 8%.
[0047] The thickener solution is selected from sodium carboxymethyl cellulose with a degree of substitution of 0.8;
[0048] Plant gum activation:
[0049] Guar gum and water were mixed at a mass ratio of 1:15 and allowed to stand at room temperature for 3 hours to swell. Then, 0.3% of the guar gum mass of endo-β-glucanase was added. The mixture was subjected to ultrasonic enzymatic hydrolysis at pH 5.0, temperature 48℃, and ultrasonic frequency 50kHz for 30 minutes. The enzyme was then inactivated by heating to 80℃ for 10 minutes. After cooling to room temperature, the mixture was discharged to obtain activated plant gum solution.
[0050] Raw material preparation:
[0051] By weight, take 100 parts of a 20% PVA solution, 120 parts of activated plant gum solution, 60 parts of an 8% thickener solution, 8 parts of a composite modifier, 0.6 parts of potassium persulfate; and 20% of the PVA solution mass of sepiolite dispersion.
[0052] The composite modifier is composed of glycerol and triethyl citrate in a mass ratio of 1.5:1.
[0053] The PVA is polyvinyl alcohol with a degree of hydrolysis of 87%, and the average degree of polymerization of the polyvinyl alcohol is 2500, and the weight-average molecular weight is 120000.
[0054] The sepiolite dispersion was obtained by mixing sepiolite and water at a mass ratio of 1:8, then adding 20% of the sepiolite mass of fumed silica, and ultrasonically dispersing at a frequency of 60kHz for 10 minutes.
[0055] Low-temperature complex reaction:
[0056] After mixing PVA solution, activated plant gum solution and sepiolite dispersion, the mixture was kept at 50℃ and stirred at 180r / min for 30min.
[0057] Add the thickener solution and continue to react for 20 minutes at a temperature of 42℃ and a stirring speed of 220r / min.
[0058] Subsequently, composite modifier and potassium persulfate were added, and the mixture was kept at 40°C and stirred at 200 r / min for 2 hours. After cooling to 25°C, it was kept at 25°C and aged for 24 hours before being discharged to obtain the mixed adhesive solution.
[0059] After the mixed adhesive solution is applied and dried, the PVA adhesive strip is obtained.
[0060] Example 2
[0061] Preparation of thickener solution:
[0062] After mixing the thickener and water in a certain mass ratio, the mixture was allowed to stand and swell for 70 minutes at a temperature of 28°C. Then, it was stirred at a low speed of 100 r / min for 35 minutes to obtain a thickener solution with a mass fraction of 9%.
[0063] The thickener solution is selected from sodium carboxymethyl cellulose with a degree of substitution of 0.85;
[0064] Plant gum activation:
[0065] Guar gum and water were mixed at a mass ratio of 1:18 and allowed to swell at room temperature for 4 hours. Then, 0.4% of the guar gum mass of endo-β-glucanase was added. The mixture was subjected to ultrasonic enzymatic hydrolysis at pH 5.1, temperature 50℃, and ultrasonic frequency 55kHz for 35 minutes. The enzyme was then inactivated by heating to 80℃ for 10 minutes. After cooling to room temperature, the mixture was discharged to obtain activated plant gum solution.
[0066] Raw material preparation:
[0067] By weight, take 110 parts of a 22% PVA solution, 125 parts of activated plant gum solution, 65 parts of a 9% thickener solution, 10 parts of a composite modifier, 0.7 parts of potassium persulfate; and a sepiolite dispersion of 22% PVA solution.
[0068] The composite modifier is composed of glycerol and triethyl citrate in a mass ratio of 1.6:1.
[0069] The PVA is polyvinyl alcohol with a degree of hydrolysis of 88%, and the average degree of polymerization of the polyvinyl alcohol is 2530, and the weight-average molecular weight is 122000.
[0070] The sepiolite dispersion was obtained by mixing sepiolite and water at a mass ratio of 1:9, then adding 22% of the sepiolite mass of fumed silica, and ultrasonically dispersing at a frequency of 60kHz for 10 minutes.
[0071] Low-temperature complex reaction:
[0072] After mixing PVA solution, activated plant gum solution and sepiolite dispersion, the mixture was kept at 52℃ and stirred at 200r / min for 35min.
[0073] Add the thickener solution and continue to react at 43°C and 240 r / min for 25 min.
[0074] Subsequently, a composite modifier and potassium persulfate were added, and the mixture was kept at 42°C and stirred at 210 r / min for 3 hours. After cooling to 25°C, it was kept at 25°C and aged for 28 hours before being discharged to obtain a mixed adhesive solution.
[0075] After the mixed adhesive solution is applied and dried, the PVA adhesive strip is obtained.
[0076] Example 3
[0077] Preparation of thickener solution:
[0078] After mixing the thickener and water in a certain mass ratio, the mixture was allowed to stand and swell for 80 minutes at 30°C, and then stirred at a low speed of 120 r / min for 45 minutes to obtain a thickener solution with a mass fraction of 10%.
[0079] The thickener solution is selected from sodium carboxymethyl cellulose with a degree of substitution of 0.9;
[0080] Plant gum activation:
[0081] Guar gum and water were mixed at a mass ratio of 1:20 and allowed to stand at room temperature for 5 hours to swell. Then, 0.5% of the guar gum mass of endo-β-glucanase was added. The mixture was subjected to ultrasonic enzymatic hydrolysis at pH 5.2, temperature 52℃, and ultrasonic frequency 60kHz for 45 minutes. The enzyme was then inactivated by heating to 80℃ for 10 minutes. After cooling to room temperature, the mixture was discharged to obtain activated plant gum solution.
[0082] Raw material preparation:
[0083] By weight, take 120 parts of a 25% PVA solution, 130 parts of activated plant gum solution, 70 parts of a 10% thickener solution, 12 parts of a composite modifier, 0.8 parts of potassium persulfate; and 25% sepiolite dispersion of the PVA solution.
[0084] The composite modifier is composed of glycerol and triethyl citrate in a mass ratio of 1.8:1.
[0085] The PVA is polyvinyl alcohol with a degree of hydrolysis of 89%, and the average degree of polymerization of the polyvinyl alcohol is 2600, and the weight-average molecular weight is 128000.
[0086] The sepiolite dispersion was obtained by mixing sepiolite and water at a mass ratio of 1:10, adding 25% of the sepiolite mass of fumed silica, and then ultrasonically dispersing the mixture at a frequency of 60kHz for 10 minutes.
[0087] Low-temperature complex reaction:
[0088] After mixing PVA solution, activated plant gum solution and sepiolite dispersion, the mixture was kept at 55℃ and stirred at 220r / min for 40min.
[0089] Add the thickener solution and continue to stir and react at 45°C and 250 r / min for 30 min.
[0090] Subsequently, composite modifier and potassium persulfate were added, and the mixture was kept at 45°C and stirred at 220 r / min for 4 hours. After cooling to 25°C, it was kept at 25°C and aged for 36 hours before being discharged to obtain the mixed adhesive solution.
[0091] After the mixed adhesive solution is applied and dried, the PVA adhesive strip is obtained.
[0092] Example 4
[0093] The difference between this embodiment and Embodiment 1 is as follows:
[0094] The degree of substitution of the sodium carboxymethyl cellulose is 0.7, and the other conditions remain unchanged.
[0095] Example 5
[0096] The difference between this embodiment and Embodiment 1 is that no fumed silica was added, while all other conditions remained unchanged.
[0097] Example 6
[0098] The difference between this embodiment and Embodiment 1 is that sepiolite was not added, while all other conditions remained unchanged.
[0099] Comparative Example 1
[0100] The difference between this comparative example and Example 1 is that the plant gum was not activated using endo-β-glucanase, while the other conditions remained basically unchanged.
[0101] Comparative Example 2
[0102] The difference between this comparative example and Example 1 is that potassium persulfate was not added, while all other conditions remained unchanged.
[0103] The performance of the products obtained in the above embodiments and comparative examples was evaluated, and the specific evaluation methods and results are as follows:
[0104] A 50µm thick PET film was used as the base film and corona treated to a dyne value of 45mN / m. The mixed adhesive solution from the examples and comparative examples was then coated onto the surface of the base film, controlling the film thickness to be 50µm after drying; the residual moisture content after drying was <3%.
[0105] According to GB / T 2792-2014, the 180° peel strength of the product was tested, and the test substrate was corrugated cardboard.
[0106] After the test is completed, the product of the corresponding embodiment or comparative example is placed at a temperature of 35°C and a relative humidity of 80% for 6 hours, and then transferred to an oven at a temperature of 60°C to dry to constant weight. After this cycle is repeated 30 times, its 180° peel strength is tested again according to the above standard.
[0107] Table 1: Peel Strength Test Results
[0108]
[0109] As can be seen from the test results in Table 1, the product obtained by the present invention not only has excellent bonding performance, but also has little impact on the bonding strength after long-term humidity changes.
[0110] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a PVA adhesive strip, characterized in that, The specific preparation steps include: Plant gum activation: Guar gum and water are mixed and swollen at a mass ratio of 1:15-20. Then, 0.3-0.5% of endo-β-glucanase by mass of guar gum is added. The mixture is subjected to sonication at pH 5.0-5.2, temperature 48-52℃, and ultrasonic frequency 50-60kHz for 30-45 minutes. The enzyme is then inactivated by heating and cooled to obtain activated plant gum solution. Raw material preparation: By weight, take 100-120 parts of PVA solution with a mass fraction of 20-25%, 120-130 parts of activated plant gum solution, 60-70 parts of thickener solution with a mass fraction of 8-10%, 8-12 parts of composite modifier, and 0.6-0.8 parts of potassium persulfate. The composite modifier is composed of glycerol and triethyl citrate in a mass ratio of 1.5-1.8:
1. Low-temperature complex reaction: After stirring and mixing the PVA solution and activated plant gum solution evenly, add the thickener solution, continue stirring and mixing evenly, add the composite modifier and potassium persulfate, keep the mixture at 40-45℃ for 2-4 hours, then age it for 24-36 hours, and then discharge the mixture to obtain the mixed gum solution. After the mixed adhesive solution is applied and dried, the PVA adhesive strip is obtained.
2. The method for preparing a PVA adhesive strip according to claim 1, characterized in that, The thickener solution is selected from any one of the following: sodium carboxymethyl cellulose solution, hydroxyethyl cellulose solution, carboxymethyl hydroxyethyl cellulose solution, and carboxymethyl hydroxypropyl cellulose solution; Furthermore, the preparation method for the thickener solution includes: After mixing the thickener and water in the specified mass ratio, allow them to stand and swell for 60-80 minutes at a temperature of 25-30℃, and then stir at a low speed of 80-120 r / min for 30-45 minutes.
3. The method for preparing a PVA adhesive strip according to claim 2, characterized in that, The thickener solution is a sodium carboxymethyl cellulose solution, wherein the degree of substitution of the sodium carboxymethyl cellulose is 0.8-0.
9.
4. The method for preparing a PVA adhesive strip according to claim 1, characterized in that, The low-temperature composite reaction also includes: The PVA solution and activated plant gum solution were kept at 50-55℃ and stirred at 180-220r / min for 30-40min. Add the thickener solution and continue to react for 20-30 minutes at a temperature of 42-45℃ and a stirring speed of 220-250 r / min. Subsequently, a composite modifier and potassium persulfate were added, and the mixture was kept at 40-45℃ and stirred at 200-220 r / min for 2-4 hours. After cooling to 25℃, it was kept at 25℃ and aged for 24-36 hours before being discharged to obtain a mixed adhesive solution.
5. The method for preparing a PVA adhesive strip according to claim 4, characterized in that, The low-temperature composite reaction also includes: After mixing PVA solution, activated plant gum solution, and sepiolite dispersion (20-25% by mass of PVA solution), the mixture is kept at 50-55℃ and stirred at 180-220 r / min for 30-40 min. The sepiolite dispersion is obtained by ultrasonic dispersion of sepiolite and water mixed at a mass ratio of 1:8-10.
6. The method for preparing a PVA adhesive strip according to claim 5, characterized in that, The sepiolite dispersion also includes 20-25% fumed silica by weight of sepiolite.
7. The method for preparing a PVA adhesive strip according to claim 1, characterized in that, The PVA is polyvinyl alcohol with a degree of hydrolysis of 87-89%, and the average degree of polymerization of the polyvinyl alcohol is 2500-2600, and the weight-average molecular weight is 120000-128000.
8. A PVA adhesive strip, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.