Antibacterial Tape Based on Oligo-Lactic Acid and Its Preparation Method

Abstract

The present invention belongs to the field of adhesive tape preparation technology, specifically relating to an antibacterial adhesive tape based on oligolactic acid and its preparation method. The antibacterial adhesive tape based on oligolactic acid comprises a backing material, an adhesive layer, and a release agent layer. The adhesive layer is provided on the upper surface of the backing material, and the release agent layer is provided on the lower surface of the backing material. The adhesive in the adhesive layer is an antibacterial adhesive made from oligolactic acid, antibacterial polylactic acid, a polyurethane elastomer, an antioxidant, and a softener. The present invention exhibits biodegradability and antibacterial properties, is beneficial to environmental protection, and can be applied in fields such as biomedicine and food packaging materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesive tape preparation, and in particular relates to an antibacterial adhesive tape based on oligolactic acid and a preparation method thereof. Background Art

[0002] The adhesive tape industry is a high-tech industry that inherits ancient fine chemical technology and gradually applies scientific and technological transformation. This type of product is extended from the medical series tape, the ancestor of adhesive tape, and is divided into six major product series: packaging series tape, trademark paper series tape, specialty tape, high-temperature resistant series tape and fashionable computer inkjet series tape. Its product application areas cover a wide range, from basic food, medicine, sanitary materials, beauty and health products, five-party supplies, cultural and educational supplies, office equipment, photographic equipment, advertising, printing, papermaking, footwear, and textiles, spanning and extending to high-tech industries such as electronics, motors, communications equipment, petroleum industry, automobile industry, shipbuilding industry and aerospace industry. It is one of the materials used in large quantities and is indispensable in daily life. However, since traditional tape products are mainly made of polyvinyl chloride, they are difficult to recycle and degrade, which greatly restricts the development of tape materials and has become a common problem faced by the world. According to incomplete statistics in 2019, the total length of tape used in my country's express delivery sector alone can reach 48 billion meters, equivalent to nearly 1,200 laps around the earth's equator. Such a huge amount of usage has brought great pressure to the degradation and processing link.

[0003] As a bio-based, environmentally friendly material, polylactic acid (PLA) is widely available, primarily from crops like corn and wheat. It completely degrades into H2O and CO2 within months to years, leaving zero soil pollution. It is a completely naturally recycled biodegradable material. PLA is used in various fields. For example, in industry and agriculture, PLA mulch films can inhibit the release of herbicides, thereby protecting crops. In the medical and biological fields, it can be used to manufacture heart stents and sterile nonwoven fabrics. In the clothing and textile industry, PLA, due to its inherent antibacterial properties, can be used to make diapers and underwear.

[0004] Chitosan is an alkaline cationic polysaccharide made by deacetylation of chitin. It is a natural antibacterial agent with broad-spectrum properties. It is a green and environmentally friendly biological antibacterial material that can promote tissue repair and wound healing. It is abundant in source, non-toxic and pollution-free. In addition to having good biocompatibility and biodegradability, it also has strong broad-spectrum antibacterial properties. It has good bactericidal effects on common pathogens represented by Escherichia coli, Staphylococcus aureus and Candida albicans. It is mainly used in food, medicine, agricultural seeds, daily chemical products, industrial wastewater treatment and other industries.

[0005] Both polylactic acid and chitosan possess excellent biocompatibility, biodegradability, and absorbability. Modified forms of both have been widely used in the medical field. By modifying the molecular structure and aggregate morphology of the polymers, the sustained-release properties, mechanical properties, biocompatibility, and degradability of the materials can be regulated, thereby creating biomedical materials with diverse applications.

[0006] Chinese patent CN113980598A discloses a method for preparing a PLA-based degradable tape, comprising uniformly stirring a mixture containing polylactic acid (PLA), polybutylene adipate-terephthalate copolymer (PBAT), starch, a crosslinking agent, and a plasticizer to obtain a mixture, extruding the mixture into a blown film, and drying the resulting semi-finished film, which serves as the substrate layer of the tape. A release layer material is coated on one side of the substrate layer to prepare a release layer, and an adhesive layer material is coated on the other side to prepare an adhesive layer. The degradable tape produced by this patent has the advantages of being environmentally friendly, having good water resistance, and flexibility; however, it has the disadvantages of having a single performance property and lacking antibacterial properties, which limits its clinical medical application.

[0007] Chinese patent CN109749646A discloses an antibacterial single-layer non-woven tape. This tape is composed of a non-woven fabric layer and an adhesive layer. The non-woven fabric is impregnated with an acidic solution of chitosan modified with trans-8-methyl-N-vanillyl-6-nonenylamide. The adhesive consists of starch, composite modified nano-tourmaline powder, succinic anhydride, hydrogen peroxide, sodium stearoyl lactylate, and deionized water. The patent's advantage lies in the uniform dispersion of the composite modified tourmaline powder in the adhesive, which imparts excellent antibacterial properties and long-lasting antibacterial properties to the tape. However, a disadvantage is that most non-woven fabrics are made from polypropylene, which is difficult to degrade naturally and is not conducive to sustainable development.

[0008] Chinese patent CN115141563A discloses a fully biodegradable tape and its preparation method. The tape's base layer is made from raw materials including polybutylene adipate / terephthalate, corn starch, polypropylene carbonate, a plasticizer, and a coupling agent. The adhesive layer is made from raw materials including oxidized starch, a diluent, a cross-linking agent, a thickener, titanium dioxide, and water. The release layer is a silicone oil release agent. The advantages of this patent are that both the base layer and the adhesive layer are made from fully biodegradable materials, maintaining the basic physical properties of the tape while also being biodegradable, making it environmentally friendly and harmless. However, the disadvantages are that the production process is relatively complex, the antibacterial function is not achieved, and the DMP, DEP, and DOP contained in the plasticizer are priority pollutants controlled by my country's environment, preventing complete environmental degradation. Summary of the Invention

[0009] The purpose of the present invention is to provide an antibacterial tape based on oligolactic acid, which has biodegradable and antibacterial properties, is beneficial to environmental protection, and can be used in the fields of biomedicine, food packaging materials, etc.; the present invention also provides a preparation method of the antibacterial tape based on oligolactic acid.

[0010] The antibacterial tape based on oligolactic acid of the present invention comprises a backing material, an adhesive layer and a release agent layer. The upper surface of the backing material is provided with an adhesive layer, and the lower surface of the backing material is provided with a release agent layer. The adhesive in the adhesive layer is an antibacterial adhesive, which is made of oligolactic acid, antibacterial polylactic acid, polyurethane elastomer, antioxidant and softener, wherein:

[0011] The preparation method of antibacterial polylactic acid comprises the following steps:

[0012] (1) Under nitrogen protection, polylactic acid and a coupling agent are added to dichloromethane and stirred for reaction, and then cooled to room temperature to obtain a mixed solution;

[0013] (2) adding diethyl ether to the mixed solution obtained in step (1) to precipitate solid powder, and filtering the precipitated solid powder to obtain polylactic acid with carbonyl imidazole end groups;

[0014] (3) Under nitrogen protection, the polylactic acid with carbonyl imidazole end groups obtained in step (2), chitosan and 4-dimethylaminopyridine are added to dimethyl sulfoxide for stirring and reacting, cooled to room temperature, and isopropanol is added to precipitate solid powder, which is then filtered to obtain antibacterial polylactic acid.

[0015] The molecular weight of the polylactic acid described in step (1) is 20,000-100,000.

[0016] The coupling agent in step (1) is N,N'-carbonyldiimidazole (CDI).

[0017] The mass ratio of the polylactic acid, coupling agent and dichloromethane described in step (1) is 40-50:30-40:80-90.

[0018] The stirring reaction temperature in step (1) is 30-60° C., and the stirring reaction time is 6-9 h.

[0019] The mass ratio of diethyl ether to coupling agent in step (2) is 40-50:30-40.

[0020] The mass ratio of chitosan, 4-dimethylaminopyridine, dimethyl sulfoxide, isopropanol and polylactic acid described in step (3) is 30-40:1-2:30-40:30-40:40-50.

[0021] The stirring reaction temperature in step (3) is 30-60° C., and the stirring reaction time is 36-72 h.

[0022] The molecular weight of the oligolactic acid is 600-1000.

[0023] The polyurethane elastomer is one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate (PPDI) or naphthalene diisocyanate (NDI).

[0024] The antioxidant is antioxidant 1076.

[0025] The softener is naphthenic oil KN-6.

[0026] The antibacterial adhesive is made of the following raw materials in parts by weight:

[0027]

[0028] The preparation method of the antibacterial adhesive comprises the following steps:

[0029] (1) Under nitrogen protection, the softener is heated and stirred to obtain a preheated softener;

[0030] (2) Under nitrogen protection, oligolactic acid, antibacterial polylactic acid, antioxidant and polyurethane elastomer are added to the preheated softener obtained in step (1), heated and mixed, discharged and cooled to obtain an antibacterial adhesive.

[0031] The heating temperature in step (1) is 80-100° C., and the stirring time is 0.5-2.5 h.

[0032] The heating temperature in step (2) is 100-120° C., and the mixing time is 1-3 h.

[0033] The release agent in the release agent layer is methyl vinyl silicone rubber.

[0034] The backing material is a polylactic acid film.

[0035] The molecular weight of the polylactic acid in the polylactic acid film is 50,000-150,000, and the thickness of the polylactic acid film is 0.05-0.15 mm.

[0036] The preparation method of the antibacterial tape based on oligolactic acid of the present invention is to first apply a release agent to one side of a backing material, then heat and soften the adhesive and then apply it to the other side of the backing material, cool to room temperature, and solidify to obtain the antibacterial tape based on oligolactic acid.

[0037] The amount of the release agent applied on the backing material is 0.5-2.5g / m 2 .

[0038] The amount of the adhesive applied on the backing material is 0.5-2.5g / m 2 .

[0039] The heating temperature is 95-105°C.

[0040] The antibacterial polylactic acid of the present invention is prepared by first cross-linking polylactic acid with highly active N,N'-carbonyldiimidazole (CDI) to obtain polylactic acid with carbonyl imidazole end groups (PLA-CI); then, under the action of catalyst 4-dimethylaminopyridine (DMAP), PLA-CI is further cross-linked with chitosan to prepare the product. Compared with polylactic acid, the antibacterial polylactic acid is chemically modified with chitosan having antibacterial activity, which is conducive to improving the antibacterial rate. Compared with the physical blend composition of polylactic acid and chitosan, the present invention uses a coupling agent to connect the two through covalent bonds to make the material system more stable, prevent the physical precipitation of components, and help improve the long-term antibacterial effect.

[0041] The preparation mechanism of antibacterial polylactic acid is as follows:

[0042]

[0043] The present invention adopts oligolactic acid as a thickener and antibacterial polylactic acid as an antibacterial active component. The antibacterial polylactic acid is prepared by connecting chitosan to polylactic acid via a covalent bond. If chitosan is used alone, chitosan has poor compatibility with other components, is prone to phase separation, and is prone to precipitation. After chitosan is connected to polylactic acid, polylactic acid has good compatibility with other components. Under the guidance of the polylactic acid structure, chitosan can also be well dispersed in the adhesive system, solving the problems of phase separation and precipitation. Polylactic acid and oligolactic acid have the same chemical structure but different molecular weights. Oligolactic acid has a small molecular weight and strong fluidity. The use of oligolactic acid is conducive to further improving the dispersibility and mutual solubility of antibacterial polylactic acid. The formula system with synergistic effects of oligolactic acid and antibacterial polylactic acid can not only obtain a tape material with stable physical and chemical properties, but also has good antibacterial activity and long-lasting antibacterial effect. The raw materials used in the preparation of the tape have good biodegradability, so the prepared tape also has good biodegradability, which provides convenience for the post-processing of the tape after use. It not only meets the special needs of the medical and health, packaging materials and other fields, but also reduces the environmental burden and meets the requirements of sustainable development.

[0044] The beneficial effects of the present invention are as follows:

[0045] (1) The surface of chitosan contains a large number of active groups such as amino and hydroxyl groups, and one of the terminal groups of polylactic acid is hydroxyl, which provides an active site for the cross-linking reaction. The two can be covalently bonded by a coupling agent to obtain antibacterial polylactic acid with a stable chemical structure, thereby improving the antibacterial activity of polylactic acid.

[0046] (2) The antibacterial polylactic acid and oligolactic acid used in the present invention have the same polylactic acid structure and have good mutual solubility according to the principle of "like dissolves like". The oligolactic acid used as a thickener has a small molecular weight and strong fluidity. The formulation system using the synergistic effect of antibacterial polylactic acid and polylactic acid is not only beneficial to improving the uniformity and stability of the adhesive, but also beneficial to regulating the viscoelasticity of the adhesive to obtain good bonding performance.

[0047] (3) The raw materials involved in the antibacterial tape based on oligolactic acid prepared by the present invention are all degradable materials. While maintaining stable chemical and physical properties, they have good biological activity and can be degraded in the natural environment. They are environmentally friendly and practical polymer materials suitable for wide promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of polylactic acid.

[0049] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of chitosan.

[0050] Figure 3 This is the H-NMR spectrum of antibacterial polylactic acid.

[0051] Figure 4 This is a comparison chart of the antibacterial polylactic acid, chitosan and polylactic acid nuclear magnetic hydrogen spectra. DETAILED DESCRIPTION

[0052] The present invention is further described below with reference to the following examples.

[0053] Example 1

[0054] The preparation method of antibacterial polylactic acid comprises the following steps:

[0055] (1) Under nitrogen protection, 40 parts of polylactic acid (molecular weight 30,000) and 30 parts of coupling agent CDI were dissolved in 80 parts of dichloromethane, stirred at 50°C for 8 hours, and then cooled to room temperature to obtain a mixed solution.

[0056] (2) 40 parts of diethyl ether were added to the mixed solution obtained in step (1) to precipitate solid powder, and the precipitated solid powder was filtered to obtain polylactic acid (PLA-CI) with carbonyl imidazole end groups.

[0057] (3) Under nitrogen protection, the PLA-CI obtained in step (2), 30 parts of chitosan, and 1 part of 4-dimethylaminopyridine (DMAP) were dissolved in 35 parts of dimethyl sulfoxide (DMSO), stirred and reacted at 50°C for 48 hours, cooled to room temperature, and 40 parts of isopropanol were added to precipitate solid powder, which was then filtered to obtain antibacterial polylactic acid.

[0058] The composition of the antibacterial adhesive is shown in Table 1.

[0059] Table 1 Composition of the antibacterial adhesive of Example 1

[0060]

[0061]

[0062] The preparation method of the antibacterial adhesive comprises the following steps:

[0063] (1) Under nitrogen protection, naphthenic oil KN-6 was added to a reaction vessel and heated to 100°C and stirred for 2 hours to obtain preheated naphthenic oil KN-6;

[0064] (2) Under nitrogen protection, oligolactic acid, antibacterial polylactic acid, antioxidant 1076 and polyurethane elastomer (TDI to MDI mass ratio is 2:1) are added to the preheated cyclohexane oil KN-6 obtained in step (1), heated to 100°C and mixed for 2 hours, discharged, and cooled to obtain an antibacterial adhesive.

[0065] The preparation method of the antibacterial tape based on oligolactic acid comprises the following steps:

[0066] (1) Use a coating machine to apply the release agent to one side of the polylactic acid film backing, with a coating amount of 0.5g / m 2 , the molecular weight of polylactic acid in the polylactic acid film is 50,000, and the film thickness of the polylactic acid film is 0.05 mm;

[0067] (2) Heat the antibacterial adhesive to 100°C to soften it and apply it to the other side of the backing material at a coating amount of 0.5g / m 2 After cooling and solidifying at room temperature, an antibacterial tape based on oligolactic acid was obtained.

[0068] Loop tack test: Using GB / T 31125-2014, the loop tack of the tape was measured to be 7.63N.

[0069] 180° peel force: Using GB / T 2792-2014, the 180° peel force of the tape was measured to be 0.569kgf.

[0070] Aging degradation test: The tape product was made into a 1cm×1cm square with a thickness of 0.1mm and placed in a small glass bottle containing a pH=8.0 phosphate buffer solution (Tris-HCl buffer system). The concentration of proteinase K (Genview) in the bottle was 0.2mg / ml. The temperature was set at 45°C and the test was carried out at a shaking speed of 140rpm. Samples were taken out at specified time intervals, washed with distilled water, and dried under vacuum until constant weight was reached. The mass of the sample was then measured. The weight loss rate (W) of the sample wasL ) is calculated by the following formula: where m o is the weight of the sample before degradation, m i is the weight of the sample after degradation. L The degradation rate was 76% after 30 days. L It is 89%.

[0071] Antibacterial performance test: The tape was cut into discs (Ø10.0 cm), the adhesive layer was rinsed and blown dry, and the antibacterial performance of the adhesive layer of the disc against three types of fungi was tested using the thin film adhesion method. The bacterial species used were Staphylococcus aureus (S. aureus ATCC29213), Escherichia coli (E. coli ATCC25922), and Candida albicans (C. albicans ATCC10231). First, the freeze-dried bacteria of each strain were mixed with Sabouraud culture medium, and 2 ml of the bacterial suspension was taken and incubated at 37°C for 24 hours. The freeze-dried bacteria were activated after being transferred twice using an inoculation loop. Then, a 1×10 5 The tape disc sample was diluted with 0.2 mL of the diluted bacterial suspension and then covered with a sterilized polyethylene film. The sample was then incubated anaerobically at 37°C (80% N2, 10% CO2, 10% H2) for 48 hours. Finally, the tape disc sample and polyethylene film were thoroughly eluted with 20 mL of a 0.9% NaCl aqueous solution. After shaking, 500 μL of the eluate was inoculated into TSA medium and incubated for 24 hours. The bacterial colonies were counted after culturing. Each group of tape disc samples was tested five times, and the average bacterial count was used to calculate the inhibition rate: inhibition rate = (number of bacteria recovered in the blank control sample - number of bacteria recovered in the experimental group sample) / number of bacteria recovered in the blank control sample × 100%. The inhibition rates for freshly prepared tape were 97.32% for S. aureus, 97.10% for E. coli, and 96.69% for C. albicans. The tape samples were subjected to accelerated aging experiments: the tape samples were stored in a constant temperature box at 55°C for 21 days. After being taken out, the above antibacterial performance test was repeated. The antibacterial rates of the tape after 21 days of aging were 94.45% against S. aureus, 93.26% against E. coli, and 93.07% against C. albicans.

[0072] Example 2

[0073] The preparation method of antibacterial polylactic acid comprises the following steps:

[0074] (1) Under nitrogen protection, 40 parts of polylactic acid (molecular weight 60,000) and 30 parts of coupling agent CDI were dissolved in 80 parts of dichloromethane, stirred at 40°C for 7 hours, and then cooled to room temperature to obtain a mixed solution.

[0075] (2) 50 parts of diethyl ether were added to the mixed solution obtained in step (1) to precipitate solid powder, and the precipitated solid powder was filtered to obtain polylactic acid (PLA-CI) with carbonyl imidazole end groups.

[0076] (3) Under nitrogen protection, the PLA-CI obtained in step (2), 40 parts of chitosan, and 2 parts of 4-dimethylaminopyridine (DMAP) were dissolved in 40 parts of dimethyl sulfoxide (DMSO), stirred and reacted at 50°C for 48 hours, cooled to room temperature, and 40 parts of isopropanol were added to precipitate solid powder, which was then filtered to obtain antibacterial polylactic acid.

[0077] The composition of the antibacterial adhesive is shown in Table 2.

[0078] Table 2 Composition of the antibacterial adhesive of Example 2

[0079]

[0080] The preparation method of the antibacterial adhesive comprises the following steps:

[0081] (1) Under nitrogen protection, naphthenic oil KN-6 was added to a reaction vessel, heated to 90°C and stirred for 1.5 hours to obtain preheated naphthenic oil KN-6;

[0082] (2) Under nitrogen protection, oligomeric lactic acid, antibacterial polylactic acid, antioxidant 1076 and TDI are added to the preheated cyclohexane oil KN-6 obtained in step (1), heated to 150° C. and mixed for 1 hour, discharged, and cooled to obtain an antibacterial adhesive.

[0083] The preparation method of the antibacterial tape based on oligolactic acid comprises the following steps:

[0084] (1) Use a coating machine to apply the release agent to one side of the polylactic acid film backing, with a coating amount of 1.5g / m 2 , the molecular weight of polylactic acid in the polylactic acid film is 80,000, and the film thickness of the polylactic acid film is 0.1 mm;

[0085] (2) Heat the antibacterial adhesive to 95°C to soften it, and apply it to the other side of the backing material at a coating amount of 1.5 g / m 2 After cooling and solidifying at room temperature, an antibacterial tape based on oligolactic acid was obtained.

[0086] Loop initial adhesion test: The test method is the same as Example 1. The measured loop initial adhesion is 7.49N;

[0087] 180° peel force: The test method is the same as in Example 1. The 180° peel force was measured to be 0.557 kgf;

[0088] Aging degradation test: The test method is the same as in Example 1. The M L The degradation rate was 70% after 30 days. L It is 88%.

[0089] Antibacterial performance testing: The testing method was the same as in Example 1. The freshly prepared tape showed an antibacterial rate of 97.89% against S. aureus, 98.01% against E. coli, and 97.69% against C. albicans. After 21 days of aging, the tape showed an antibacterial rate of 95.19% against S. aureus, 94.13% against E. coli, and 94.72% against C. albicans.

[0090] Example 3

[0091] The preparation method of antibacterial polylactic acid comprises the following steps:

[0092] (1) Under nitrogen protection, 40 parts of polylactic acid (molecular weight 80,000) and 40 parts of coupling agent CDI were dissolved in 90 parts of dichloromethane, stirred at 60°C for 9 hours, and then cooled to room temperature to obtain a mixed solution.

[0093] (2) 50 parts of diethyl ether were added to the mixed solution obtained in step (1) to precipitate solid powder, and the precipitated solid powder was filtered to obtain polylactic acid (PLA-CI) with carbonyl imidazole end groups.

[0094] (3) Under nitrogen protection, the PLA-CI obtained in step (2), 40 parts of chitosan, and 2 parts of 4-dimethylaminopyridine (DMAP) were dissolved in 40 parts of dimethyl sulfoxide (DMSO), stirred and reacted at 60°C for 72 hours, cooled to room temperature, and 40 parts of isopropanol were added to precipitate solid powder, which was then filtered to obtain antibacterial polylactic acid.

[0095] The composition of the antibacterial adhesive is shown in Table 3.

[0096] Table 3 Composition of the antibacterial adhesive of Example 3

[0097]

[0098] The preparation method of the antibacterial adhesive comprises the following steps:

[0099] (1) Under nitrogen protection, naphthenic oil KN-6 was added to a reaction vessel, heated to 80°C and stirred for 2.5 hours to obtain preheated naphthenic oil KN-6;

[0100] (2) Under nitrogen protection, oligolactic acid, antibacterial polylactic acid, antioxidant 1076 and polyurethane elastomer (PPDI to NDI mass ratio of 5:1) are added to the preheated cyclohexane oil KN-6 obtained in step (1), heated to 120°C and mixed for 3 hours, discharged, and cooled to obtain an antibacterial adhesive.

[0101] The preparation method of the antibacterial tape based on oligolactic acid comprises the following steps:

[0102] (1) Use a coating machine to apply the release agent to one side of the polylactic acid film backing, with a coating amount of 2g / m 2 , the molecular weight of polylactic acid in the polylactic acid film is 150,000, and the film thickness of the polylactic acid film is 0.15 mm;

[0103] (2) Heat the antibacterial adhesive to 105°C to soften it and apply it to the other side of the backing material at a coating amount of 2g / m 2 After cooling and solidifying at room temperature, an antibacterial tape based on oligolactic acid was obtained.

[0104] Loop initial adhesion test: The test method is the same as Example 1. The measured loop initial adhesion is 7.56N;

[0105] 180° peel force: The test method is the same as in Example 1. The 180° peel force was measured to be 0.560 kgf;

[0106] Aging degradation test: The test method is the same as in Example 1. The M L The degradation rate was 73% after 30 days. L It is 89%.

[0107] Antibacterial performance testing: The testing method was the same as in Example 1. The freshly prepared tape showed an antibacterial rate of 97.72% against S. aureus, 97.81% against E. coli, and 97.12% against C. albicans. After 21 days of aging, the tape showed an antibacterial rate of 94.79% against S. aureus, 93.88% against E. coli, and 92.95% against C. albicans.

[0108] Comparative Example 1

[0109] The composition of the antibacterial adhesive is shown in Table 4.

[0110] Table 4 Composition of the antibacterial adhesive of Comparative Example 1

[0111]

[0112] The preparation method of the antibacterial adhesive comprises the following steps:

[0113] (1) Under nitrogen protection, naphthenic oil KN-6 was added to a reaction vessel and heated to 100°C and stirred for 2 hours to obtain preheated naphthenic oil KN-6;

[0114] (2) Under nitrogen protection, oligolactic acid, polylactic acid, chitosan, antioxidant 1076 and polyurethane elastomer (TDI to MDI mass ratio is 2:1) are added to the preheated cyclohexane oil KN-6 obtained in step (1), heated to 100°C and mixed for 2 hours, discharged, and cooled to obtain an antibacterial adhesive.

[0115] Other steps are the same as in Example 1.

[0116] Loop tack test: The test method is the same as in Example 1. The measured loop tack is 5.45N.

[0117] 180° peel force: The test method is the same as that of Example 1. The 180° peel force was measured to be 0.296 kgf.

[0118] Aging degradation test: The test method is the same as that in Example 1. The ML after 7 days of degradation is 82%, and the ML after 30 days of degradation is 94%.

[0119] Antibacterial performance testing: The testing method was the same as in Example 1. The freshly prepared tape showed an antibacterial rate of 84.61% against S. aureus, 83.93% against E. coli, and 83.51% against C. albicans. After 21 days of aging, the tape showed an antibacterial rate of 58.82% against S. aureus, 58.01% against E. coli, and 57.40% against C. albicans.

[0120] Results analysis: Compared with Example 1, the annular initial adhesion and 180° peel strength of the antibacterial tape in Comparative Example 1 were reduced, mainly because the chitosan component was added to the adhesive system through physical blending, and its compatibility with other components was relatively poor, thus affecting the bonding performance. The antibacterial rate of the newly prepared tape was reduced because chitosan had poor compatibility with other components of the adhesive. When used alone, chitosan had poor dispersibility in the adhesive system, was prone to phase separation, and was prone to precipitation. During the rinsing step of the sample pretreatment for the antibacterial performance test, chitosan was partially removed, resulting in a reduced antibacterial rate. After aging of the tape, the adhesive system was more prone to phase separation and chitosan precipitation. More chitosan was removed during the rinsing step of the sample pretreatment for the antibacterial performance test, so the antibacterial rate of the tape was lower after 21 days of aging. Compared with Example 1, the degradation rate of the tape in Comparative Example 1 was accelerated because the chitosan was free from the adhesive system, resulting in a reduction in its physical stability, which was reflected in the accelerated degradation rate.

[0121] Comparative Example 2

[0122] No antibacterial polylactic acid is added to the composition of the antibacterial adhesive, and the other steps are the same as those in Example 1.

[0123] Loop tack test: The test method is the same as in Example 1. The measured loop tack is 7.30N.

[0124] 180° peel force: The test method is the same as that of Example 1. The 180° peel force was measured to be 0.538 kgf.

[0125] Aging degradation test: The test method is the same as in Example 1. The M L The degradation rate was 78% after 30 days. L is 90%.

[0126] Antibacterial Performance Test: The testing method was the same as in Example 1. The freshly prepared tape showed an antibacterial rate of 24.51% against S. aureus, 23.07% against E. coli, and 25.16% against C. albicans. After 21 days of aging, the tape showed an antibacterial rate of 11.68% against S. aureus, 10.40% against E. coli, and 10.42% against C. albicans.

[0127] Results Analysis: Compared with Example 1, the loop tack and 180° peel strength of the antibacterial tape in Comparative Example 2 showed little change, indicating that the antibacterial polylactic acid had no significant effect on adhesive properties. The newly prepared tape exhibited a significantly lower antibacterial rate due to the absence of antibacterial polylactic acid, the primary antibacterial active component. The weak antibacterial effect stemmed from the oligolactic acid in the tape. The antibacterial rate of the tape decreased slightly after 21 days of aging because the oligolactic acid is easily decomposed, and the decomposition products were removed during the pretreatment rinse step for the antibacterial test, resulting in a lower measured antibacterial rate.

[0128] Comparative Example 3

[0129] Oligomeric lactic acid was not added to the composition of the antibacterial adhesive, and the other steps were the same as in Example 1.

[0130] Loop tack test: The test method is the same as in Example 1. The measured loop tack is 3.93N.

[0131] 180° peel force: The test method is the same as that of Example 1. The 180° peel force was measured to be 0.144 kgf.

[0132] Aging degradation test: The test method is the same as in Example 1. The M L The degradation rate was 70% after 30 days. L It is 81%.

[0133] Antibacterial Performance Test: The testing method was the same as in Example 1. The freshly prepared tape showed an antibacterial rate of 87.16% against S. aureus, 86.53% against E. coli, and 86.90% against C. albicans. After 21 days of aging, the tape showed an antibacterial rate of 75.72% against S. aureus, 76.08% against E. coli, and 75.99% against C. albicans.

[0134] Results Analysis: Compared with Example 1, the loop tack and 180° peel strength of the antibacterial tape in Comparative Example 3 were significantly reduced. This is due to the lack of oligolactic acid, a tackifier. This component regulates the viscoelasticity of the adhesive layer, and an imbalance in viscoelasticity can lead to decreased bonding performance. Compared with Example 1, the antibacterial rate of the freshly prepared tape was reduced. This is because when oligolactic acid and antibacterial polylactic acid are used in conjunction, oligolactic acid can improve the dispersibility and miscibility of the antibacterial polylactic acid. In the absence of oligolactic acid, the antibacterial polylactic acid is not uniformly dispersed in the adhesive system, resulting in a lower measured antibacterial rate. Due to the lack of uniform dispersion of the antibacterial polylactic acid, the antibacterial polylactic acid was partially removed during the sample pretreatment rinsing step of the antibacterial performance test in the aged tape, resulting in a lower measured antibacterial rate. Compared with Example 1, the degradation rate of Comparative Example 3 was reduced because oligolactic acid is the most easily degradable component in the tape, and therefore, the degradation rate would be reduced if oligolactic acid is not added.

[0135] Comparative Example 4

[0136] No polyurethane elastomer is added to the composition of the antibacterial adhesive, and the other steps are the same as in Example 1.

[0137] Loop tack test: The test method is the same as in Example 1. The measured loop tack is 3.50N.

[0138] 180° peel force: The test method is the same as that of Example 1. The 180° peel force was measured to be 0.133 kgf.

[0139] Aging degradation test: The test method is the same as in Example 1. The M L The degradation rate was 78% after 30 days. L is 90%.

[0140] Antibacterial performance testing: The testing method was the same as in Example 1. The freshly prepared tape showed an antibacterial rate of 97.88% against S. aureus, 97.15% against E. coli, and 97.73% against C. albicans. After 21 days of aging, the tape showed an antibacterial rate of 94.36% against S. aureus, 94.55% against E. coli, and 93.05% against C. albicans.

[0141] Results Analysis: Compared with Example 1, the loop tack and 180° peel strength of the antibacterial tape in Comparative Example 4 were significantly reduced. This is due to the imbalance in the viscoelastic ratio of the adhesive layer caused by the absence of the polyurethane elastomer, resulting in reduced adhesive performance. Compared with Example 1, the antibacterial rate of the freshly prepared tape and the antibacterial rate of the aged tape did not change significantly, indicating that the polyurethane elastomer has little effect on the antibacterial activity. The degradation rate also did not change significantly compared with Example 1, indicating that the polyurethane elastomer has little effect on the degradable properties of the tape.

[0142] The test results of the adhesive tape properties of Examples 1-3 are shown in Table 4, and the test results of the adhesive tape properties of Comparative Examples 1-4 are shown in Table 5.

[0143] Table 4 Adhesive tape performance test results of Examples 1-3

[0144]

[0145]

[0146] Table 5 Test results of adhesive tape performance of comparative examples 1-4

[0147]

[0148] Using nuclear magnetic resonance ( 1 The chemical structures of polylactic acid, chitosan and antibacterial polylactic acid were analyzed by H NMR, and the solvent used was CDCl3.

[0149] Polylactic acid 1 H NMR spectrum is shown in Figure 1 , its structural formula is as follows:

[0150]

[0151] The carboxyl hydrogen at position 1 was located at 5.36 ppm, the hydroxyl hydrogen at position 6 was located at 4.15 ppm, the hydrogen at positions 4 and 5 was located at 5.15 ppm, and the hydrogen at positions 2 and 3 was located at 1.57 ppm.

[0152] Chitosan 1 H NMR spectrum is shown in Figure 2 , its structural formula is as follows:

[0153]

[0154] The hydrogen at the 1-position was located at 1.68 ppm, the hydrogen at the 2-position was located at 1.26 ppm, the hydrogen at the 3-position was located at 2.36 ppm, the hydrogen at the 4-position was located at 2.56 ppm, and the hydrogen at the 5-position was located at 5.76 ppm.

[0155] Antibacterial polylactic acid1 H NMR spectrum is shown in Figure 3 The hydroxyl hydrogen originally located at 4.15ppm in polylactic acid disappears, which is due to the cross-linking reaction between the hydroxyl group in polylactic acid and CDI; the number of amino hydrogen originally located at 1.68ppm in chitosan decreases and shifts to the right to 1.41ppm. This is because the amino group in chitosan undergoes a cross-linking reaction with PLA-CI, so chitosan and polylactic acid are connected through carbonyl groups, and there are a large number of ester groups on the polylactic acid chain with strong electron-withdrawing effects, causing the absorption peak of chitosan to shift to the right. From the analysis of the figure, the characteristic peaks belonging to polylactic acid are 5.25ppm and 1.22ppm, and the characteristic peaks belonging to chitosan are 5.86ppm, 2.01ppm, 2.22ppm, and 1.41ppm.

[0156] By comparing the NMR spectra of polylactic acid, chitosan and antibacterial polylactic acid, Figure 4 As shown, the absorption peak indicated by the arrow at A is the methyl hydrogen on the polylactic acid polymer chain. It is found that the absorption peak is shifted to the right by 0.35 ppm. The absorption peak indicated by the arrow at B is the amino group in chitosan. The number of amino hydrogen decreases and shifts to the right by 0.27 ppm, indicating that chitosan and polylactic acid are successfully connected, and the two are connected through the carbonyl group.

Claims

1. An antibacterial tape based on oligolactic acid, comprising a backing material, an adhesive layer and a release agent layer, wherein the adhesive layer is provided on the upper surface of the backing material and the release agent layer is provided on the lower surface of the backing material, characterized in that The adhesive in the adhesive layer is an antibacterial adhesive, which is made of oligolactic acid, antibacterial polylactic acid, polyurethane elastomer, antioxidant and softener, wherein: The preparation method of antibacterial polylactic acid comprises the following steps: (1) Under nitrogen protection, polylactic acid and coupling agent are added to dichloromethane and stirred for reaction, and then cooled to room temperature to obtain a mixed solution; (2) adding diethyl ether to the mixed solution obtained in step (1) to precipitate solid powder, and filtering the precipitated solid powder to obtain polylactic acid with carbonyl imidazole end groups; (3) Under nitrogen protection, the polylactic acid with carbonyl imidazole end groups obtained in step (2), chitosan and 4-dimethylaminopyridine are added to dimethyl sulfoxide for stirring and reacting, cooled to room temperature, and isopropanol is added to precipitate solid powder, which is then filtered to obtain antibacterial polylactic acid; The coupling agent in step (1) is N,N'-carbonyldiimidazole; The molecular weight of the oligolactic acid is 600-1000, and the polyurethane elastomer is one or more of toluene diisocyanate, diphenylmethane diisocyanate, p-phenylene diisocyanate or naphthalene diisocyanate; The antibacterial adhesive is made of the following raw materials in parts by weight: 50-60 parts of oligolactic acid 20-30 parts of antibacterial polylactic acid 20-30 parts polyurethane elastomer 0.2-0.6 parts of antioxidant 10-15 parts softener.

2. The antibacterial tape based on oligolactic acid according to claim 1, characterized in that The molecular weight of the polylactic acid described in step (1) is 20,000-100,000, the mass ratio of polylactic acid, coupling agent and dichloromethane is 40-50:30-40:80-90, the stirring reaction temperature is 30-60°C, and the stirring reaction time is 6-9h.

3. The antibacterial tape based on oligolactic acid according to claim 1, characterized in that The mass ratio of diethyl ether to coupling agent in step (2) is 40-50:30-40.

4. The antibacterial tape based on oligolactic acid according to claim 1, characterized in that The mass ratio of chitosan, 4-dimethylaminopyridine, dimethyl sulfoxide, isopropanol and polylactic acid in step (3) is 30-40:1-2:30-40:30-40:40-50, the stirring reaction temperature is 30-60°C, and the stirring reaction time is 36-72h.

5. The antibacterial tape based on oligolactic acid according to claim 1, characterized in that The antioxidant is antioxidant 1076, and the softener is naphthenic oil KN-6.

6. The antibacterial tape based on oligolactic acid according to claim 1, characterized in that The preparation method of the antibacterial adhesive comprises the following steps: (1) Under nitrogen protection, the softener is heated and stirred to obtain a preheated softener; (2) Under nitrogen protection, oligolactic acid, antibacterial polylactic acid, antioxidant and polyurethane elastomer are added to the preheated softener obtained in step (1), heated and mixed, discharged, and cooled to obtain an antibacterial adhesive.

7. The antibacterial tape based on oligolactic acid according to claim 1, characterized in that The release agent in the release agent layer is methyl vinyl silicone rubber, and the backing material is polylactic acid film.

8. A method for preparing an antibacterial tape based on oligolactic acid according to any one of claims 1 to 7, characterized in that First, the release agent is applied to one side of the backing material, and then the adhesive is heated and softened and then applied to the other side of the backing material. The adhesive is cooled to room temperature and solidified to obtain an antibacterial tape based on oligolactic acid.

9. The method for preparing an antibacterial tape based on oligolactic acid according to claim 8, characterized in that The heating temperature is 95-105°C.

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