A bio-based acrylic pressure sensitive adhesive and a method of making the same

Abstract

The application discloses a kind of bio-based acrylic pressure-sensitive adhesive and preparation method thereof, belong to pressure-sensitive adhesive technical field, the acrylic pressure-sensitive adhesive, count by weight parts, including 45~90 parts bio-based soft monomer, 15~35 parts bio-based hard monomer, 10~20 parts bio-based functional monomer, 5~15 parts modified bio-based nanofiber, 3~6 parts natural crosslinking agent, 80~150 parts solvent and 0.05~1 parts initiator;Wherein, the modified bio-based nanofiber is the natural spider silk nanofiber modified by nano silver;The natural crosslinking agent is secoiridoid compound.Modified spider silk nanofiber can improve the strength and toughness of acrylic pressure-sensitive adhesive, enhance the cohesive strength of pressure-sensitive adhesive, thereby improve peel strength;Seccoiridoid compound can form three-dimensional network structure by chemical reaction with bio-based functional monomer, and then improve tackiness;The addition of nano silver also makes the antibacterial ability of pressure-sensitive adhesive have some promotion.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure-sensitive adhesives, and in particular relates to a bio-based acrylic pressure-sensitive adhesive and a preparation method thereof. Background Art

[0002] Pressure-sensitive adhesives (PSAs), also known as self-adhesive adhesives, are a class of polymer materials with long-term bonding properties. These materials quickly form a stable bond with substrates using only slight pressure, without the need for heat, solvents, or chemical reactions. Due to their advantages of easy bonding, ease of removal, repeatable bonding, and stability in both standard and harsh environments, PSA has found widespread application in consumer goods, electronics, construction, chemicals, pharmaceuticals, automotive, and aerospace industries.

[0003] Currently, in addition to rubber-based and silicone-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are the most commonly used type. Acrylic pressure-sensitive adhesives are often prepared using petroleum-based monomers. However, with the acceleration of industrialization, demand for this vital resource, petroleum, has continued to rise. Petroleum is not only an indispensable fuel source for daily life but also the foundation of many key industries, including chemicals and transportation. However, in recent decades, the gradual depletion of global oil resources has become an indisputable fact. This has not only limited the supply of oil but also driven up its market price. Affected by oil price fluctuations, the price of acrylic pressure-sensitive adhesives, which rely on petrochemicals, has also increased. Furthermore, acrylic compounds synthesized from petroleum monomers are often difficult to degrade and pose a significant environmental risk. From a long-term development perspective, new, sustainable materials offer greater development prospects.

[0004] Biomass resources are becoming an important raw material for obtaining clean energy and high-value chemicals due to their abundant reserves and renewable nature, and are receiving increasing attention. Currently, researchers have begun to explore methods for using biomass resources to prepare pressure-sensitive adhesives, aiming to develop new materials that are more environmentally friendly and sustainable. This research direction not only helps to reduce dependence on traditional petrochemical resources, but also provides new development opportunities for the pressure-sensitive adhesive industry. For example, the Chinese patent with authorization announcement number CN115785862B discloses a bio-based anti-warping acrylic pressure-sensitive adhesive and a preparation method thereof. The invention uses acrylic acid and polyfarnesylene glycol as bio-based functional monomers to prepare a bio-based acrylic resin. Polyfarnesylene glycol contains double bonds and -OH, which can be used for free radical polymerization and cross-linking with a curing agent to form a network structure, thereby ensuring the cohesive strength and anti-warping properties of the pressure-sensitive adhesive. For example, Chinese patent application CN111621241A discloses a method for preparing a biodegradable bio-based acrylic pressure-sensitive adhesive protective film. The bio-based (meth)acrylate monomers in this invention are primarily derived from pine resin and natural plant oils, with a bio-based carbon content of no less than 70%. This invention uses easily degradable, environmentally friendly raw materials. However, compared to acrylic pressure-sensitive adhesives made from petroleum-based monomers, bio-based acrylic pressure-sensitive adhesives still suffer from poor adhesion, weather resistance, and antibacterial and mildew resistance, which shortens their service life. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a bio-based acrylic pressure-sensitive adhesive and a preparation method thereof. The bio-based acrylic pressure-sensitive adhesive not only uses bio-based raw materials instead of petroleum-based raw materials, but also has a simple preparation method and is easy to operate.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A bio-based acrylic pressure-sensitive adhesive, comprising, by weight, 45 to 90 parts of a bio-based soft monomer, 15 to 35 parts of a bio-based hard monomer, 10 to 20 parts of a bio-based functional monomer, 5 to 15 parts of modified bio-based nanofibers, 3 to 6 parts of a natural cross-linking agent, 80 to 150 parts of a solvent, and 0.05 to 1 part of an initiator;

[0008] Wherein, the modified bio-based nanofiber is a spider silk nanofiber modified by nanosilver; and the natural cross-linking agent is an cyclopentadiene compound.

[0009] The present invention uses bio-based soft monomers, bio-based hard monomers and bio-based functional monomers as the main components of the bio-based acrylic pressure-sensitive adhesive. The bio-based soft monomers are selected from acrylate monomers with longer side chains. The long side chains increase the flexibility of the polymer and lower the glass transition temperature (Tg) of the polymer, so that the adhesive can still maintain good adhesion performance at lower temperatures; the bio-based hard monomers are selected from acrylate or methacrylate monomers with shorter side chains or no side chains. The addition of hard monomers can significantly improve the cohesion of the pressure-sensitive adhesive, making it less likely to undergo cohesive failure under high temperature conditions, and the short side chain or no side chain structure of the hard monomers increases the rigidity of the polymer; the bio-based functional monomers contain double bonds and carboxyl groups, so that they can react better with crosslinking agents.

[0010] Preferably, the bio-based soft monomer is any one of 2-ethylhexyl acrylate, 2-octyl acrylate, and n-butyl acrylate; the bio-based hard monomer is selected from isobornyl methacrylate or methyl acrylate; and the bio-based functional monomer is acrylic acid.

[0011] Preferably, the iridoid compound is genipin; the solvent is any one of dimethyl sulfoxide, ethyl acetate, and isopropanol; and the initiator is azobisisobutyronitrile or benzoyl peroxide.

[0012] Spider silk, or simply spider silk, is known for its incredible strength and elasticity, earning it the nickname "biological steel." Its exceptional strength and lightness make it highly valuable for applications in aviation, military equipment, and personal protection. Spider silk is typically golden, transparent, and shiny, with a physical density of approximately 1.13 to 1.29 g / cm. 3It has a high breaking energy, strong UV resistance, and is resistant to both high and low temperatures. Thermal analysis by researchers has shown that Nephila spider silk exhibits excellent thermal stability below 200°C, hardens only above 300°C, remains elastic at -40°C, and becomes brittle only at extremely low temperatures. As a natural product, spider silk is completely biodegradable, which is highly consistent with current green environmental protection concepts. Spider silk is primarily composed of a series of different types of proteins, collectively known as spidroins. Spidroins are primarily composed of amino acids such as glycine (Gly), alanine (Al a), serine (Ser), and proline (Pro). They contain highly repetitive amino acid sequences, typically consisting of β-sheets composed of alanine and A-helices rich in proline. These repetitive sequences give spidroins their high elasticity and strength. Recombinant spider silk can currently be produced using genetic recombination techniques, but its mechanical properties cannot compare to those of natural spider silk. The spider silk used in the present invention is from the golden-spinning spider, a genus of the Araneae family. This large-bodied arthropod, with female spiders measuring 35 to 50 mm, can weave large webs exceeding one meter in diameter. The spider silk's excellent mechanical properties enhance the tear resistance of the pressure-sensitive adhesive, making it less susceptible to breakage when subjected to external forces.

[0013] Nanosilver has excellent broad-spectrum antimicrobial properties, effectively inhibiting the growth of a wide range of bacteria, fungi, and viruses. Using nanosilver to modify spider silk, the modified solution is then used to create a nanofiber membrane through electrospinning. This allows the nanosilver to fill the tiny gaps within the spider silk nanofibers, enhancing the overall density of the nanofibers and further improving their strength and wear resistance. The modified spider silk nanofibers not only significantly increase the cohesive strength of the pressure-sensitive adhesive, but also impart excellent antimicrobial properties, thereby extending its service life.

[0014] Genipin, also known as 5-hydroxy-1,4-naphthoquinone-2-β-D-glucoside, is a natural compound extracted from Gardenia fruit and belongs to the class of cyclopentadiene ether terpenoid compounds. Genipin, which contains multiple hydroxyl groups, has a wide range of biological activities and can be used as an excellent natural cross-linking agent. It can be cross-linked with materials such as proteins, gelatin, and chitosan as biomaterials for use in medical and health fields. In the present invention, genipin is used as a cross-linking agent for acrylic pressure-sensitive adhesives. The hydroxyl groups in genipin can react with the carboxyl groups in bio-based acrylic functional monomers to form ester bonds, thereby forming a dense cross-linked network in the pressure-sensitive adhesive, enhancing the internal bonding tightness and improving the cohesion. The brief reaction equation involved is shown below:

[0015]

[0016] As a general technical concept, the present invention also provides a method for preparing a bio-based acrylic pressure-sensitive adhesive, such asFigure 1 As shown, the following steps are included:

[0017] Step (1), adding a bio-based soft monomer, a bio-based hard monomer, a bio-based functional monomer and a first part of an initiator into a reactor containing a first part of a solvent, wherein the first part of the solvent accounts for 50 to 70% of the total amount of the solvent, and the first part of the initiator accounts for 35 to 65% of the total amount of the initiator, heating and stirring for 10 to 30 minutes, condensing, and then refluxing and keeping warm to obtain a solution A;

[0018] Step (2), adding genipin and modified natural spider silk nanofibers to the remaining solvent, and stirring with ultrasound to obtain solution B;

[0019] Step (3), when the temperature of solution A in step (1) drops to the set temperature, solution B prepared in step (2) is added to solution A, stirred evenly, and the remaining initiator is added, the temperature is raised to react, and then refluxed and kept warm. After the reaction is completed, the solution is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0020] Preferably, in step (1), the heating temperature is 68-94° C., and the reflux holding time is 3-8 h.

[0021] Preferably, in step (2), ultrasonic stirring is performed three times, each time for 10 to 20 minutes; and in step (3), solution A is cooled to 50°C, then heated to 60 to 75°C, and refluxed for 1 to 5 hours. Ultrasonic stirring allows the modified spider silk nanofibers to be evenly dispersed in the pressure-sensitive adhesive.

[0022] Preferably, the preparation method of the modified natural spider silk nanofiber comprises the following steps:

[0023] Step (1), washing the natural spider silk with deionized water to remove excess impurities, drying, chopping, and placing in a reactor containing 10 to 30 mL of a fluorinated solvent, stirring at room temperature until the spider silk is completely dissolved, and filtering to obtain a natural spider silk protein solution after the dissolution is complete;

[0024] Step (2), adding silver nitrate solution to step (1), stirring, and obtaining a natural spider silk protein solution modified with nanosilver;

[0025] Step (3), injecting the nanosilver-modified natural spider silk protein solution obtained in step (2) into an electrospinning apparatus, starting electrospinning, and obtaining nanosilver-modified natural spider silk nanofibers.

[0026] Preferably, in step (1), the drying temperature is 40-60°C, the drying time is 3-8 hours, the fluorinated solvent is hexafluoroisopropanol, and the stirring time is 6-10 hours. Hexafluoroisopropanol (HFIP) is a polar organic solvent with strong dissolving power. Spider silk is a natural fiber composed of proteins, which contain a large number of hydrogen bonds and other non-covalent interactions. HFIP can disrupt the hydrogen bond network within the spider silk protein and effectively dissolve the spider silk.

[0027] Preferably, in step (2), the amount of silver nitrate used is 4-8% of the mass of natural spider silk, and the stirring time is 1-4 hours.

[0028] Preferably, in step (3), the electrospinning parameters are: voltage 12-20 kV, receiving distance 6-18 cm, and injection speed 40-80 μL / min.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention adds spider silk nanofibers modified with nanosilver. The tightly packed secondary structure of the spider silk protein contained in the spider silk makes it a semi-crystalline molecular spring structure, which determines its extremely high tensile strength and elastic modulus. The spider silk nanofibers play the role of skeleton support in the bio-based pressure-sensitive adhesive, greatly improving the cohesion and tensile strength of the pressure-sensitive adhesive, thereby improving the peel strength. In addition, the spider silk's own UV resistance and high and low temperature resistance properties give the pressure-sensitive adhesive good weather resistance; the nanosilver itself has a broad spectrum of antibacterial activity and can efficiently and quickly inhibit or kill various bacteria, fungi and viruses. This makes the prepared pressure-sensitive adhesive have good antibacterial properties. When nanosilver is used to modify spider silk nanofibers, the intermolecular heterogeneity between nanosilver and spider silk nanofibers can effectively avoid the agglomeration of spider silk fibers, making the spider silk nanofibers more evenly dispersed in the acrylic pressure-sensitive adhesive, maintaining the consistency of the entire system; at the same time, due to the high specific surface area characteristics brought by the size effect of nanosilver, it can fill the tiny gaps or defective areas inside the spider silk nanofibers. The two are coupled with each other, increasing the overall density of the spider silk nanofibers, and when subjected to external force, nanosilver as a "filler" can offset part of the stress, thereby improving the overall strength and fracture resistance of the spider silk nanofibers, and then strengthening the cohesion of the pressure-sensitive adhesive, making it less likely to peel off.

[0031] (2) Genipin is added as a natural crosslinking agent in the present invention. Genipin molecules can undergo a crosslinking reaction with acrylic acid to form stable covalent bonds, forming a dense three-dimensional crosslinked network, further improving the crosslinking density of the pressure-sensitive adhesive and increasing its viscosity. Furthermore, as a natural compound, genipin itself has certain antioxidant properties and can scavenge free radicals, which helps to delay the aging of the pressure-sensitive adhesive and maintain its long-term functional stability.

[0032] (3) The components used in the present invention use bio-based raw materials instead of petroleum raw materials, which is economical and environmentally friendly, reduces the risk of environmental pollution, and is in line with the development trend of green chemistry, which is more conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of preparing bio-based acrylic pressure-sensitive adhesive. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described in detail below. The described embodiments are only some embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the scope of protection of the present invention. The present invention is further described below in conjunction with specific embodiments.

[0035] Unless otherwise specified, the various components and chemical reagents used in the examples of the present invention were obtained through conventional commercial channels:

[0036] 2-Ethylhexyl acrylate, 2-octyl acrylate, and n-butyl acrylate were purchased from Tesco Chemical (Hubei) Co., Ltd.

[0037] Isobornyl methacrylate and methyl acrylate were from Sigma-Aldrich (Shanghai) Biotechnology Co., Ltd.

[0038] Acrylic acid was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0039] Dimethyl sulfoxide, ethyl acetate, and isopropanol were purchased from Sinopharm Group.

[0040] Spider silk comes from Hainan Spider King Biotechnology Co., Ltd.

[0041] Genipin is from Shaanxi Saien Biotechnology Co., Ltd.

[0042] Example 1

[0043] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 90 parts 2-octyl acrylate, 30 parts isobornyl methacrylate, 10 parts acrylic acid, 5 parts nanosilver-modified spider silk nanofibers, 6 parts genipin, 150 parts dimethyl sulfoxide, and 0.06 parts azobisisobutyronitrile. The specific preparation process includes the following steps:

[0044] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 50°C and dried for 5 h. After drying, the silk was chopped into pieces and placed in a vial containing 20 mL of HFIP. The silk was stirred with a magnetic stirrer for 8 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0045] (2) adding 0.03 parts of silver nitrate solution to the mixture in step (1) and stirring for 3 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0046] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 60 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to be 15 kV, and the distance from the needle to the receiver was 10 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0047] (4) 90 parts of dimethyl sulfoxide, 90 parts of 2-octyl acrylate, 30 parts of isobornyl methacrylate, 10 parts of acrylic acid, and 0.03 parts of azobisisobutyronitrile were added to a four-necked flask, and the mixture was slowly heated to 86°C in a constant temperature water bath, stirred for 20 minutes, and then condensed. The system was refluxed and kept warm for 6 hours to obtain solution A;

[0048] (5) 6 parts of genipin and 5 parts of the natural spider silk nanofibers modified with nanosilver prepared in step (3) were placed in a conical flask containing 60 parts of dimethyl sulfoxide, and ultrasonically stirred 3 times for 15 minutes each time to obtain solution B;

[0049] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.03 parts of azobisisobutyronitrile is added thereto, and the temperature is raised to 65° C., followed by reflux and heat preservation for 3 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0050] Example 2

[0051] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 60 parts 2-octyl acrylate, 22 parts methyl acrylate, 15 parts acrylic acid, 10 parts nanosilver-modified spider silk nanofibers, 3 parts genipin, 100 parts ethyl acetate, and 1 part azobisisobutyronitrile. The specific preparation process includes the following steps:

[0052] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 40°C and dried for 3 h. After drying, the silk was chopped into pieces and placed in a vial containing 30 mL of HFIP. The silk was stirred with a magnetic stirrer for 10 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0053] (2) adding 0.4 parts of silver nitrate solution to the mixture in step (1) and stirring for 1 hour to obtain a natural spider silk protein solution modified with nanosilver;

[0054] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 40 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to be 12 kV, and the distance from the needle to the receiver was 6 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0055] (4) Add 50 parts of ethyl acetate, 60 parts of 2-octyl acrylate, 22 parts of methyl acrylate, 15 parts of acrylic acid, and 0.65 parts of azobisisobutyronitrile to a four-necked flask, slowly heat to 88°C in a constant temperature water bath, stir for 15 minutes, and then condense. The system is refluxed and kept warm for 8 hours to obtain solution A.

[0056] (5) 3 parts of genipin and 10 parts of the natural spider silk nanofibers modified with nanosilver prepared in step (3) were placed in a conical flask containing 50 parts of ethyl acetate, and ultrasonically stirred 3 times for 10 minutes each time to obtain solution B;

[0057] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.35 parts of azobisisobutyronitrile are added thereto, and the temperature is raised to 60° C., followed by reflux and heat preservation for 5 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0058] Example 3

[0059] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 45 parts of 2-octyl acrylate, 15 parts of isobornyl methacrylate, 12 parts of acrylic acid, 15 parts of nanosilver-modified spider silk nanofibers, 4 parts of genipin, 80 parts of isopropyl alcohol, and 0.05 parts of benzoyl peroxide. The specific preparation process includes the following steps:

[0060] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 60°C and dried for 8 h. After drying, the silk was chopped into pieces and placed in a vial containing 10 mL of HFIP. The silk was stirred with a magnetic stirrer for 6 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0061] (2) adding 0.75 parts of silver nitrate solution to the mixture in step (1) and stirring for 4 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0062] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 80 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to 20 kV, and the distance from the needle to the receiver was 18 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0063] (4) In a four-necked flask, 56 parts of isopropyl alcohol, 45 parts of 2-octyl acrylate, 15 parts of isobornyl methacrylate, 12 parts of acrylic acid, and 0.00175 parts of benzoyl peroxide were added. The mixture was slowly heated to 68°C in a constant temperature water bath and stirred for 30 minutes. The mixture was then condensed and refluxed and kept warm for 3 hours to obtain solution A.

[0064] (5) 4 parts of genipin and 15 parts of the natural spider silk nanofibers modified with nanosilver prepared in step (3) were placed in a conical flask containing 24 parts of isopropanol, and ultrasonically stirred 3 times for 20 minutes each time to obtain solution B;

[0065] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.04825 parts of benzoyl peroxide are added thereto, and the temperature is raised to 75° C., followed by reflux and heat preservation for 2 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0066] Example 4

[0067] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 80 parts of 2-ethylhexyl acrylate, 25 parts of isobornyl methacrylate, 20 parts of acrylic acid, 7 parts of nanosilver-modified spider silk nanofibers, 5 parts of genipin, 120 parts of dimethyl sulfoxide, and 0.09 parts of azobisisobutyronitrile. The specific preparation process includes the following steps:

[0068] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 45°C for 4 h. After drying, the silk was chopped into pieces and placed in a vial containing 15 mL of HFIP. The silk was stirred with a magnetic stirrer for 7 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0069] (2) adding 0.42 parts of silver nitrate solution to the mixture in step (1) and stirring for 3.5 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0070] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 75 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to 18 kV, and the distance from the needle to the receiver was 14 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0071] (4) 84 parts of dimethyl sulfoxide, 80 parts of 2-ethylhexyl acrylate, 25 parts of isobornyl methacrylate, 20 parts of acrylic acid, and 0.036 parts of azobisisobutyronitrile were added to a four-necked flask, and the mixture was slowly heated to 70°C in a constant temperature water bath, stirred for 20 minutes, and then condensed. The system was refluxed and kept warm for 5 hours to obtain solution A;

[0072] (5) 5 parts of genipin and 7 parts of the natural spider silk nanofiber modified with nanosilver prepared in step (3) were placed in a conical flask containing 36 parts of dimethyl sulfoxide, and ultrasonically stirred 3 times for 12 minutes each time to obtain solution B;

[0073] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.054 parts of azobisisobutyronitrile are added thereto, and the temperature is raised to 62° C., followed by reflux and heat preservation for 3 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0074] Example 5

[0075] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 75 parts 2-ethylhexyl acrylate, 23 parts methyl acrylate, 13 parts acrylic acid, 8 parts nanosilver-modified spider silk nanofibers, 4 parts genipin, 130 parts ethyl acetate, and 0.08 parts azobisisobutyronitrile. The specific preparation process includes the following steps:

[0076] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 55°C and dried for 5 h. After drying, the silk was chopped into pieces and placed in a vial containing 25 mL of HFIP. The silk was stirred with a magnetic stirrer for 6.5 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0077] (2) adding 0.4 parts of silver nitrate solution to the mixture in step (1) and stirring for 2.5 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0078] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 45 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to be 14 kV, and the distance from the needle to the receiver was 12 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0079] (4) 71.5 parts of ethyl acetate, 75 parts of 2-ethylhexyl acrylate, 23 parts of methyl acrylate, 13 parts of acrylic acid, and 0.032 parts of azobisisobutyronitrile were added to a four-necked flask, slowly heated to 90°C in a constant temperature water bath, and stirred for 12 minutes before condensation. The system was refluxed and kept warm for 7 hours to obtain solution A.

[0080] (5) 4 parts of genipin and 8 parts of the natural spider silk nanofibers modified with nanosilver prepared in step (3) were placed in a conical flask containing 58.5 parts of ethyl acetate, and ultrasonically stirred 3 times for 14 minutes each time to obtain solution B;

[0081] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.048 parts of azobisisobutyronitrile is added thereto, and the temperature is raised to 62° C., followed by reflux and heat preservation for 4.5 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0082] Example 6

[0083] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 50 parts 2-ethylhexyl acrylate, 16 parts isobornyl methacrylate, 14 parts acrylic acid, 12 parts nanosilver-modified spider silk nanofibers, 3 parts genipin, 90 parts isopropyl alcohol, and 0.5 parts benzoyl peroxide. The specific preparation process includes the following steps:

[0084] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 48°C and dried for 4.5 h. After drying, the silk was chopped into pieces and placed in a vial containing 22 mL of HFIP. The silk was stirred with a magnetic stirrer for 5.5 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0085] (2) adding 0.84 parts of silver nitrate solution to the mixture in step (1) and stirring for 1.5 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0086] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 55 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to be 13 kV, and the distance from the needle to the receiver was 11 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0087] (4) Add 58.5 parts of isopropyl alcohol, 50 parts of 2-ethylhexyl acrylate, 16 parts of isobornyl methacrylate, 14 parts of acrylic acid, and 0.3 parts of benzoyl peroxide to a four-necked flask, slowly heat to 72°C in a constant temperature water bath, stir for 25 minutes, and then condense. The system is refluxed and kept warm for 4.5 hours to obtain solution A.

[0088] (5) 3 parts of genipin and 12 parts of the natural spider silk nanofibers modified with nanosilver prepared in step (3) were placed in a conical flask containing 31.5 parts of isopropanol, and ultrasonically stirred 3 times for 13 minutes each time to obtain solution B;

[0089] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.2 parts of benzoyl peroxide is added thereto, and the temperature is raised to 64° C., followed by reflux and heat preservation for 2.5 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0090] Example 7

[0091] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 65 parts n-butyl acrylate, 21 parts isobornyl methacrylate, 14 parts acrylic acid, 9 parts nanosilver-modified spider silk nanofibers, 6 parts genipin, 110 parts dimethyl sulfoxide, and 0.4 parts azobisisobutyronitrile. The specific preparation process includes the following steps:

[0092] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 46°C and dried for 7.5 h. After drying, the silk was chopped into pieces and placed in a vial containing 18 mL of HFIP. The silk was stirred with a magnetic stirrer for 8.5 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0093] (2) adding 0.45 parts of silver nitrate solution to the mixture in step (1) and stirring for 2.5 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0094] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 63 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to 16 kV, and the distance from the needle to the receiver was 13 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0095] (4) 72.6 parts of dimethyl sulfoxide, 65 parts of n-butyl acrylate, 21 parts of isobornyl methacrylate, 14 parts of acrylic acid, and 0.16 parts of azobisisobutyronitrile were added to a four-necked flask, slowly heated to 77°C in a constant temperature water bath, and stirred for 20 minutes before condensation. The system was refluxed and kept warm for 5.5 hours to obtain solution A;

[0096] (5) 6 parts of genipin and 9 parts of the natural spider silk nanofibers modified with nanosilver prepared in step (3) were placed in a conical flask containing 37.4 parts of dimethyl sulfoxide, and ultrasonically stirred 3 times for 11 minutes each time to obtain solution B;

[0097] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.24 parts of azobisisobutyronitrile are added thereto, and the temperature is raised to 73° C., followed by reflux and heat preservation for 3.5 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0098] Example 8

[0099] A bio-based acrylic pressure-sensitive adhesive is prepared from the following raw materials in parts by weight: 76 parts n-butyl acrylate, 23 parts methyl acrylate, 11 parts acrylic acid, 6 parts nanosilver-modified spider silk nanofibers, 5 parts genipin, 140 parts ethyl acetate, and 0.1 part azobisisobutyronitrile. The specific preparation process includes the following steps:

[0100] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 44°C and dried for 6 h. After drying, the silk was chopped into pieces and placed in a vial containing 16 mL of HFIP. The silk was stirred with a magnetic stirrer for 9 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0101] (2) adding 0.33 parts of silver nitrate solution to the mixture in step (1) and stirring for 3 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0102] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 74 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to be 17 kV, and the distance from the needle to the receiver was 8 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0103] (4) 67.2 parts of ethyl acetate, 76 parts of n-butyl acrylate, 23 parts of methyl acrylate, 11 parts of acrylic acid, and 0.04 parts of azobisisobutyronitrile were added to a four-necked flask, slowly heated to 92°C in a constant temperature water bath, and stirred for 18 minutes before condensation. The system was refluxed and kept warm for 7.5 hours to obtain solution A;

[0104] (5) 5 parts of genipin and 8 parts of the nanosilver-modified spider silk nanofibers prepared in step (3) were placed in a conical flask containing 72.8 parts of ethyl acetate, and ultrasonically stirred 3 times for 16 minutes each time to obtain solution B;

[0105] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.06 parts of azobisisobutyronitrile are added thereto, and the temperature is raised to 66° C., followed by reflux and heat preservation for 4.5 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0106] Example 9

[0107] A bio-based acrylic pressure-sensitive adhesive is made from the following raw materials in parts by weight: 85 parts n-butyl acrylate, 27 parts isobornyl methacrylate, 14 parts acrylic acid, 13 parts nanosilver-modified spider silk nanofibers, 4 parts genipin, 135 parts isopropyl alcohol, and 0.07 parts benzoyl peroxide. The specific preparation process includes the following steps:

[0108] (1) Fresh spider silk was washed with deionized water to remove excess impurities. The washed spider silk was placed in an oven at 42°C and dried for 7.5 h. After drying, the silk was chopped into pieces and placed in a vial containing 12 mL of HFIP. The silk was stirred with a magnetic stirrer for 9.5 h to dissolve the silk. The dissolved solution was filtered through a filter to obtain a natural spider silk protein solution.

[0109] (2) adding 0.728 parts of silver nitrate solution to the mixture in step (1) and stirring for 4 hours to obtain a natural spider silk protein solution modified with nanosilver;

[0110] (3) placing the nanosilver-modified natural spider silk protein solution obtained in step (2) into an injection syringe, and extruding it at a rate of 55 μL / min through a microinjection pump. During the spinning process, the voltage was controlled to be 15 kV, and the distance from the needle to the receiver was 9 cm, thereby obtaining nanosilver-modified natural spider silk nanofibers;

[0111] (4) 86.4 parts of isopropyl alcohol, 85 parts of n-butyl acrylate, 27 parts of isobornyl methacrylate, 14 parts of acrylic acid, and 0.0364 parts of benzoyl peroxide were added to a four-necked flask, slowly heated to 74°C in a constant temperature water bath, and stirred for 24 minutes before condensation. The system was refluxed and kept warm for 4.5 hours to obtain solution A;

[0112] (5) 4 parts of genipin and 13 parts of the natural spider silk nanofibers modified with nanosilver prepared in step (3) were placed in a conical flask containing 48.6 parts of isopropanol, and ultrasonically stirred 3 times for 18 minutes each time to obtain solution B;

[0113] (6) After solution A is cooled to 50° C., solution B obtained in step (5) is added thereto, and the remaining 0.04336 parts of benzoyl peroxide are added thereto, and the temperature is raised to 68° C., followed by reflux and heat preservation for 2.5 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

[0114] Comparative Example 1

[0115] A bio-based acrylic pressure-sensitive adhesive is the same as Example 1 except that it does not contain natural spider silk nanofibers modified with nano-silver.

[0116] Comparative Example 2

[0117] A bio-based acrylic pressure-sensitive adhesive is the same as Example 1 except that it does not contain genipin.

[0118] Comparative Example 3

[0119] A bio-based acrylic pressure-sensitive adhesive is the same as Example 1 except that it does not contain nanosilver.

[0120] The products prepared in Examples 1-9 and the bio-based pressure-sensitive adhesive prepared in Comparative Examples 1-3 were coated on a PE T base film with a thickness of 80 μm, dried at 120°C for 3 min to obtain a pressure-sensitive adhesive tape with a dry adhesive thickness of 50 μm. The tape was cured using a UV curing machine for 40 seconds, and its performance was tested.

[0121] First, the adhesiveness and durability of the pressure-sensitive tape were tested, using the standards GB / T 2792-2014 for 180° peel strength and GB / T 4851-2017 for initial tack. The test results are shown in Table 1.

[0122] Table 1 Viscosity and durability test results of Examples 1 to 9 and Comparative Examples 1 to 3

[0123]

[0124]

[0125] 180° peel force (N / 25mm) and tack retention at 20°C are important parameters for evaluating the adhesion and durability of pressure-sensitive adhesives. 180° peel force refers to the force required to peel the pressure-sensitive adhesive from the substrate at an angle of 180°, reflecting the adhesion strength between the pressure-sensitive adhesive and the substrate. A higher peel force means a stronger adhesion. Tack retention refers to the ability of a pressure-sensitive adhesive to maintain adhesion under specific temperature and time conditions. It is usually tested under standard conditions of 20°C to evaluate its long-lasting adhesion at room temperature. As can be seen from Table 1, Examples 1 to 9 provided by the present invention have high peel strength and good long-lasting adhesion performance. The tack retention at 20°C can all be maintained for more than 72 hours without displacement, which can ensure its long-term working performance. Compared with Examples 1 to 9, Comparative Example 1 does not contain natural spider silk nanofibers modified with nanosilver, and its 180° peel force is only 6.3N / 25mm, which is smaller than the minimum 11.7N / 25mm in the embodiment, and the adhesion at 20°C is much less than 72h, indicating that the addition of modified natural spider silk nanofibers can effectively enhance the adhesion and durability of the pressure-sensitive adhesive; similarly, Comparative Example 2 does not contain genipin, and its 180° peel force is only 67.2N / 25mm, which is higher than Comparative Example 1, but still less than 11.7N / 25mm, and the adhesion at 20°C is much less than 72h, indicating that genipin can also improve the adhesion and service life of the pressure-sensitive adhesive.

[0126] The antibacterial properties of the pressure-sensitive adhesive were then tested, using Escherichia coli and Staphylococcus aureus as the test bacteria. The pressure-sensitive adhesives prepared in Examples 1 to 9 and Comparative Examples 1 to 3 were immersed in water for 72 hours according to GB / T 20944-2007, and their antibacterial properties were tested. The specific results are shown in Table 2.

[0127] Table 2 Antibacterial performance test results of Examples 1 to 9 and Comparative Examples 1 to 3

[0128]

[0129]

[0130] As shown in Table 2, the pressure-sensitive adhesives prepared in Examples 1 to 9 of the present invention have good antibacterial properties, with antibacterial rates against Escherichia coli and Staphylococcus aureus both exceeding 98%. After immersion in water for 72 hours, the antibacterial rates against Escherichia coli and Staphylococcus aureus remain above 96.5%, indicating that the pressure-sensitive adhesives prepared in the present invention have good and long-lasting antibacterial effects. The pressure-sensitive adhesive in Comparative Example 3, which does not contain nanosilver, has significantly lower initial antibacterial properties and antibacterial properties after immersion in water for 72 hours than those in Examples 1 to 9, indicating that nanosilver helps improve the antibacterial properties of the pressure-sensitive adhesive.

[0131] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A bio-based acrylic pressure-sensitive adhesive, characterized in that: The acrylic pressure-sensitive adhesive comprises, by weight, 45 to 90 parts of a bio-based soft monomer, 15 to 35 parts of a bio-based hard monomer, 10 to 20 parts of a bio-based functional monomer, 5 to 15 parts of modified bio-based nanofibers, 3 to 6 parts of a natural cross-linking agent, 80 to 150 parts of a solvent, and 0.05 to 1 part of an initiator. The modified bio-based nanofibers are natural spider silk nanofibers modified by nanosilver; the natural crosslinking agent is genipin; and the genipin is added by ultrasonically stirring a solution obtained by mixing genipin and natural spider silk nanofibers modified by nanosilver.

2. The bio-based acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The bio-based soft monomer is any one of 2-ethylhexyl acrylate and n-butyl acrylate; the bio-based hard monomer is selected from isobornyl methacrylate or methyl acrylate; and the bio-based functional monomer is acrylic acid.

3. The bio-based acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The solvent is selected from any one of dimethyl sulfoxide, ethyl acetate, and isopropyl alcohol; and the initiator is azobisisobutyronitrile or benzoyl peroxide.

4. A method for preparing a bio-based acrylic pressure-sensitive adhesive according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step (1) adding a bio-based soft monomer, a bio-based hard monomer, a bio-based functional monomer and a first part of an initiator into a reactor containing a first part of a solvent, wherein the first part of the solvent accounts for 50-70% of the total amount of the solvent, and the first part of the initiator accounts for 35-65% of the total amount of the initiator, heating and stirring for 10-30 minutes, condensing, and then refluxing and keeping warm to obtain a solution A; Step (2), adding genipin and modified natural spider silk nanofibers to the remaining solvent, and stirring with ultrasound to obtain solution B; Step (3), when the temperature of solution A in step (1) drops to the set temperature, solution B prepared in step (2) is added to solution A, stirred evenly, and the remaining initiator is added, the temperature is raised to react, and then refluxed and kept warm. After the reaction is completed, the solution is cooled to room temperature to obtain a bio-based acrylic pressure-sensitive adhesive.

5. The method for preparing a bio-based acrylic pressure-sensitive adhesive according to claim 4, characterized in that: In the step (1), the heating temperature is 68-94° C., and the reflux holding time is 3-8 h.

6. The method for preparing a bio-based acrylic pressure-sensitive adhesive according to claim 4, characterized in that: In the step (2), ultrasonic stirring is performed three times, each time for 10 to 20 minutes; in the step (3), the temperature of solution A is reduced to 50°C, then raised to 60 to 75°C, and refluxed for 1 to 5 hours.

7. The method for preparing a bio-based acrylic pressure-sensitive adhesive according to claim 4, characterized in that: The preparation method of the modified natural spider silk nanofiber comprises the following steps: Step (1), washing the natural spider silk with deionized water, drying it, chopping it into pieces and placing it into a reactor containing a fluorinated solvent, stirring it thoroughly at room temperature until the spider silk is completely dissolved, and filtering it after the dissolution is complete to obtain a natural spider silk protein solution; Step (2), adding silver nitrate solution to step (1), stirring, and obtaining a natural spider silk protein solution modified with nanosilver; Step (3), injecting the nanosilver-modified natural spider silk protein solution obtained in step (2) into an electrospinning apparatus, starting electrospinning, and obtaining nanosilver-modified natural spider silk nanofibers.

8. The method for preparing a bio-based acrylic pressure-sensitive adhesive according to claim 7, characterized in that: In the step (1), the drying temperature is 40-60° C., and the drying time is 3-8 h. The fluorinated solvent is hexafluoroisopropanol, the amount used is 10-30 mL, and the stirring time is 6-10 h.

9. The method for preparing a bio-based acrylic pressure-sensitive adhesive according to claim 7, wherein: In step (2), the amount of silver nitrate used is 4-8% of the mass of natural spider silk, and the stirring time is 1-4 hours.

10. The method for preparing a bio-based acrylic pressure-sensitive adhesive according to claim 7, characterized in that: In step (3), the electrospinning parameters are: voltage 12-20 kV, receiving distance 6-18 cm, and injection speed 40-80 μL / min.

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