Transparent polylactic acid film with antibacterial property, ultraviolet aging resistance and high toughness as well as preparation method and application of transparent polylactic acid film

Abstract

The invention provides a transparent polylactic acid film with antibacterial, anti-ultraviolet aging and high toughness, and a preparation method and application thereof, the transparent polylactic acid film comprises the following raw materials by weight: 80-99 parts of polylactic acid, 10-20 parts of poly (methacrylic acid-2, 2, 6, 7-tetramethyl-4-piperidine-2, 2, 6, 7-tetramethyl-4-piperidine-2, 6, 7-tetramethyl-4-piperidine-2 1 to 20 parts of 2, 2, 6, 6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)-poly (butyl acrylate) nano microspheres, 0.5 to 2 parts of a lubricant and 0.2 to 0.4 part of an antioxidant. According to the polylactic acid film, the poly (methacrylic acid-2, 2, 6, 6-tetramethyl-4-piperidinyl ester-co-methyl methacrylate)-poly (butyl acrylate) nano microspheres are adopted, so that the polylactic acid film has high toughness and also has antibacterial property, ultraviolet aging resistance and high transparency.

Description

Technical Field

[0001] The present invention belongs to the technical field of polylactic acid films, and particularly relates to a transparent polylactic acid film with antibacterial, anti-ultraviolet aging and high toughness, and a preparation method and application thereof. Background Art

[0002] At present, the vast majority of polymer materials are derived from non-renewable fossil resources. Their huge production and consumption have led to a large consumption of petroleum resources and an increasing amount of plastic waste. Therefore, it is imperative to research and promote biodegradable polymer materials. Among many bio-based biodegradable polymer materials, polylactic acid is a biodegradable polymer material synthesized from lactic acid, the fermentation product of corn or sugarcane. It can be decomposed into carbon dioxide and water by the action of microorganisms in soil or water, without causing environmental pollution, and can replace traditional non-degradable petroleum-based polymer materials in many fields. Polylactic acid (PLA) is used in packaging materials, disposable lunch boxes, bone nails, surgical instruments and other materials due to its good biocompatibility and biodegradability. However, polylactic acid itself has the disadvantages of poor toughness, poor impact resistance and low melt strength, which are not conducive to forming and processing, thus limiting the practical application of polylactic acid.

[0003] Scholars at home and abroad have conducted a large number of studies on the toughening modification of polylactic acid. At present, the toughening modification of polylactic acid is mainly divided into two categories: chemical modification and physical modification. Among them, the chemical method can achieve toughening by copolymerizing flexible chain segments to destroy the regularity of the polylactic acid chain and reduce the crystallinity, but the cost is relatively high and it is not suitable for industrial production. Physical modification is a toughening method of polylactic acid that has been studied more in recent years. The method of physical modification is simple, economical and effective. By selecting appropriate blending components, adjusting the ratio between the two components, improving the compatibility of the components and using different material forming and processing methods, etc., new materials that meet various requirements can be obtained. In physical blending, methods such as using plasticizers, toughening agents or blending with other polymers can be used to improve its mechanical properties. Among them, blending with a toughening agent is a good method to improve the mechanical properties of polylactic acid. Common toughening agents for PLA include: methyl methacrylate-butadiene-styrene copolymer, ethylene-octene copolymer grafted with glycidyl methacrylate, methyl methacrylate-butadiene-glycidyl methacrylate copolymer, and butyl acrylate-ethyl acrylate-glycidyl methacrylate copolymer, etc. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a transparent polylactic acid film with antibacterial, anti-ultraviolet aging and high toughness, and a preparation method and application thereof. The polylactic acid film has excellent mechanical properties, such as high Young's modulus, tensile strength and elongation at break; it also has excellent antibacterial property, anti-ultraviolet aging property and high transparency.

[0005] The present invention provides a transparent polylactic acid film with antibacterial, anti-ultraviolet aging and high toughness. By weight, it comprises the following raw materials:

[0006] 80 - 99 parts of polylactic acid, 1 - 20 parts of poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres, 0.5 - 2 parts of lubricant and 0.2 - 0.4 parts of antioxidant.

[0007] Preferably, the poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres have a polybutyl acrylate core and a copolymer shell of 2,2,6,6-tetramethyl-4-piperidyl methacrylate and methyl methacrylate.

[0008] Preferably, the poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres are prepared by the following method:

[0009] Heat the polybutyl acrylate emulsion to 70 - 80 °C, remove oxygen, add a radical initiator, and then dropwise add a mixed solution of methyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate, and cure to obtain a cured product;

[0010] Add the cured product to a demulsifier, precipitate the polymer, filter, wash with water, and dry to obtain poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres.

[0011] Preferably, the mass ratio of polybutyl acrylate, methyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate in the polybutyl acrylate emulsion is (100 - 110):(3 - 3.3):(1 - 1.1).

[0012] Preferably, the curing temperature is 70 - 75 °C and the curing time is 110 - 130 min.

[0013] Preferably, the radical initiator is selected from potassium persulfate or ammonium persulfate;

[0014] The demulsifier is selected from aqueous magnesium sulfate solution, aqueous sodium chloride solution or aqueous aluminum sulfate solution.

[0015] Preferably, the lubricant is selected from erucamide and ethylene bisstearamide;

[0016] The antioxidant is selected from tris(2,4-di-tert-butylphenyl) phosphite and pentaerythritol tetrakis[(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

[0017] Preferably, the transparent polylactic acid film material comprises the following raw materials:

[0018] 80 - 99 parts of polylactic acid, 1 - 20 parts of poly(methyl methacrylate - 2,2,6,6 - tetramethyl - 4 - piperidyl ester - co - methyl methacrylate)@polybutyl acrylate nanospheres, 0.5 - 1.0 part of erucamide, 0.5 - 1.0 part of ethylene bisstearamide, 0.1 - 0.2 part of tris(2,4 - di - tert - butylphenyl) phosphite, and 0.1 - 0.2 part of pentaerythritol tetrakis[(3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate].

[0019] The present invention provides a method for preparing a transparent polylactic acid film having antibacterial, anti - ultraviolet aging and high toughness as described in the above technical solution, comprising the following steps:

[0020] Mix polylactic acid, poly(methyl methacrylate - 2,2,6,6 - tetramethyl - 4 - piperidyl ester - co - methyl methacrylate)@polybutyl acrylate nanospheres, lubricant and antioxidant uniformly, then extrude and pelletize, and blow - mold to obtain a transparent polylactic acid film having antibacterial, anti - ultraviolet aging and high toughness.

[0021] The present invention provides an application of the transparent polylactic acid film having antibacterial, anti - ultraviolet aging and high toughness as described in the above technical solution in medical waste packaging bags, food preservative films, food packaging, agricultural mulch films or inner lining films of trash cans.

[0022] The present invention provides a transparent polylactic acid film having antibacterial, anti - ultraviolet aging and high toughness. By weight, it comprises the following raw materials: 80 - 99 parts of polylactic acid, 1 - 20 parts of poly(methyl methacrylate - 2,2,6,6 - tetramethyl - 4 - piperidyl ester - co - methyl methacrylate)@polybutyl acrylate nanospheres, 0.5 - 2 parts of lubricant, and 0.2 - 0.4 parts of antioxidant. By adopting poly(methyl methacrylate - 2,2,6,6 - tetramethyl - 4 - piperidyl ester - co - methyl methacrylate)@polybutyl acrylate nanospheres, the polylactic acid film has high toughness, and also has antibacterial, anti - ultraviolet aging and high transparency. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of P(TMPMA - co - MMA)@PBA nanospheres;

[0024] Figure 2 It is a particle size distribution diagram of PBA and P(TMPMA - co - MMA)@PBA nanospheres;

[0025] Figure 3 It is a transmission electron microscope image of PBA nanospheres;

[0026] Figure 4 It is a transmission electron microscopy image of P(TMPMA-co-MMA)@PBA nanospheres. Specific embodiments

[0027] The present invention provides a transparent polylactic acid film material with antibacterial, anti-ultraviolet aging and high toughness. By weight, it includes the following raw materials:

[0028] 80-99 parts of polylactic acid, 1-20 parts of poly(methyl acrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres, 0.5-2 parts of lubricant, and 0.2-0.4 parts of antioxidant.

[0029] The preparation raw materials of the transparent polylactic acid film material provided by the present invention include 80-99 parts of polylactic acid, and the specific amounts are 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, 98 parts or 99 parts; the physical and chemical parameters of the polylactic acid (Zhejiang Hisun Biomaterials Co., Ltd., model REVODE110; M w : 1.8×10 5 g / mol; PDI: 1.41; MFI: 12 g / 10 min, 210 °C). In specific embodiments, the model of the polylactic acid is REVODE110.

[0030] The preparation raw materials of the transparent polylactic acid film material provided by the present invention include 1-20 parts of poly(methyl acrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres, and the specific amounts are 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts or 20 parts.

[0031] In the present invention, the poly(methyl acrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres have a polybutyl acrylate core and a copolymer of methyl acrylate-2,2,6,6-tetramethyl-4-piperidyl ester and methyl methacrylate as the shell.

[0032] The above-mentioned impact modifier with a "core-shell" structure in this application is an ideal toughening agent. The "core" in its structure can endow the matrix with toughness, and the methyl methacrylate in the "shell" copolymer can not only maintain the shape of the core-shell particles but also has good compatibility with the polylactic acid matrix, enabling the impact modifier to be well dispersed in the matrix.

[0033] In the "shell" layer copolymer of the core-shell structured haloamine precursor nanospheres, 2,2,6,6-tetramethyl-4-piperidyl methacrylate is a haloamine antibacterial agent, which has high-efficiency broad-spectrum bactericidal properties. At the same time, it has a stable structure and overcomes the disadvantage of poor heat resistance of small molecule antibacterial agents, providing more new methods for the preparation and application of haloamine antibacterial agents. In addition, 2,2,6,6-tetramethyl-4-piperidyl methacrylate in the "shell" layer copolymer also enables the film to exhibit extremely excellent anti-ultraviolet aging performance. Under long-term ultraviolet irradiation, it can still effectively resist the invasion of ultraviolet rays, slow down the aging speed of the material to the greatest extent, and ensure the stability of the various properties of the material. At the same time, the composite material where it is located also performs excellently. On the basis of having excellent anti-ultraviolet ability, it still perfectly maintains high transparency, allowing light to pass through unobstructed, which not only ensures the practical value but also takes into account the aesthetic requirements, providing an ideal choice for many application scenarios with strict requirements for material properties.

[0034] In the present invention, the poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres are prepared according to the following method:

[0035] Heat the polybutyl acrylate emulsion to 70-80 °C, remove oxygen, add a radical initiator, and then dropwise add a mixed solution of methyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate, and cure to obtain a cured product;

[0036] Add the cured product to a demulsifier, precipitate the polymer, filter, wash with water, and dry to obtain poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres.

[0037] In the present invention, the polybutyl acrylate (PBA) emulsion is preferably prepared according to the following method:

[0038] Mix an emulsifier, a pH regulator and water, heat to 70-80 °C, remove oxygen, add triallyl isocyanurate and butyl acrylate, after 30 min, add an aqueous solution of potassium persulfate (KPS), and continue the reaction for 18-23 min after the solution turns blue; then dropwise add a pre-emulsified mixture containing butyl acrylate, triallyl isocyanurate, sodium dodecyl sulfate and water, add an aqueous solution of potassium persulfate once every 55-60 min, and continue the reaction and cure for 110-130 min after the addition is completed to obtain a polybutyl acrylate emulsion.

[0039] In the present invention, the emulsifier is selected from sodium dodecyl sulfate and sodium dodecylbenzenesulfonate; the pH regulator is selected from sodium carbonate, sodium phosphate or sodium bicarbonate.

[0040] In the present invention, the mass ratio of butyl acrylate, methyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate in the butyl acrylate emulsion is (100 - 110):(3 - 3.3):(1 - 1.1), preferably 100:3:1.

[0041] In the present invention, it is preferred to remove oxygen by continuously introducing argon or nitrogen.

[0042] In the present invention, the temperature of curing is 70 - 75 °C and the time of curing is 110 - 130 min.

[0043] In the present invention, the free radical initiator is selected from potassium persulfate or ammonium persulfate; the free radical initiator is an aqueous solution (1%) of 30 g.

[0044] In the present invention, the mixed solution of methyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate is mixed with the butyl acrylate emulsion in a dropping manner, and the dropping rate is 0.4 rpm.

[0045] In the present invention, the demulsifier is selected from aqueous magnesium sulfate solution, aqueous sodium chloride solution, aqueous aluminum sulfate solution; the addition amount of the demulsifier is an aqueous solution (0.5%) of 1 L. In the specific examples of the present invention, the concentration of the aqueous magnesium sulfate solution is 0.5%.

[0046] In the present invention, the precipitated polymer is filtered with a filter cloth; the number of times of washing with water is 1 - 5 times, preferably 2 - 3 times; drying is carried out in a vacuum drying oven, the drying temperature is 45 - 55 °C and the time is 22 - 26 h.

[0047] The raw materials for preparing the polylactic acid film provided by the present invention include 0.5 - 2 parts of lubricant and 0.2 - 0.4 parts of antioxidant. The specific amounts of the lubricant are 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1.0 part, 1.1 part, 1.2 part, 1.3 part, 1.4 part, 1.5 part, 1.6 part, 1.7 part, 1.8 part, 1.9 part or 2.0 parts; the specific amounts of the antioxidant are 0.2 part, 0.25 part, 0.3 part, 0.35 part or 0.4 part. In the present invention, the lubricant is selected from erucamide and ethylene bisstearamide; the antioxidant is selected from tris(2,4-di-tert-butylphenyl) phosphite and pentaerythritol tetrakis[(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

[0048] The transparent polylactic acid film in the present invention comprises the following raw materials:

[0049] 80 - 99 parts of polylactic acid, 1 - 20 parts of poly(2,2,6,6 - tetramethyl - 4 - piperidyl methacrylate - co - methyl methacrylate)@polybutyl acrylate nanospheres, 0.5 - 1.0 part of erucamide, 0.5 - 1.0 part of ethylene bisstearamide, 0.1 - 0.2 part of tris(2,4 - di - tert - butylphenyl) phosphite, and 0.1 - 0.2 part of pentaerythritol tetrakis[(3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate].

[0050] In a specific embodiment of the present invention, the transparent polylactic acid film comprises the following raw materials:

[0051] PLA: 83.8 parts, P(TMPMA - co - MMA)@PBA: 15 parts, EA: 0.5 part, EBS: 0.5 part, antioxidant 168: 0.1 part, and antioxidant 1010: 0.1 part;

[0052] Or PLA: 88.8 parts, P(TMPMA - co - MMA)@PBA: 10 parts, EA: 0.5 part, EBS: 0.5 part, antioxidant 168: 0.1 part, and antioxidant 1010: 0.1 part;

[0053] Or 77.6 parts, P(TMPMA - co - MMA)@PBA: 20 parts, EA: 1.0 part, EBS: 1.0 part, antioxidant 168: 0.2 part, and antioxidant 1010: 0.2 part.

[0054] The novel high - toughness polylactic acid film provided by the present invention brings new solutions to many industries. The film provided by the present invention has many remarkable characteristics. It has excellent antibacterial ability and can effectively kill various pathogenic bacteria such as Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, and Candida albicans, providing a safe and reliable guarantee for fields such as food packaging and medical supplies, and greatly reducing the risk of bacterial growth. Moreover, it also exhibits excellent anti - ultraviolet aging performance. Under long - term ultraviolet irradiation, it can still maintain stable physical and chemical properties and will not easily age or become brittle, effectively extending the service life of the product. It is worth mentioning that the transparency of the film is extremely high (transparency > 90%), and light can pass through almost unobstructed. This characteristic not only provides a good display effect for the packaged products, enabling consumers to clearly see the products at a glance, but also meets the strict requirements for material transparency in some optical application fields, taking into account both aesthetics and practicality while ensuring functionality.

[0055] The present invention provides a preparation method of the transparent polylactic acid film material with antibacterial, anti - ultraviolet aging, and high - toughness as described in the above technical solution, comprising the following steps:

[0056] After uniformly mixing polylactic acid, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres, a lubricant, and an antioxidant, they are extruded and granulated, and then blow-molded to obtain a transparent polylactic acid film material with antibacterial, anti-ultraviolet aging, and high toughness.

[0057] In the present invention, external cold air with a temperature of 18 - 23 °C is blown out of the film bubble by a blower; the barrel temperatures in different regions of the film blowing machine are set to 170 - 190 °C, and the screw rotation speed is set to 35 - 45 rpm; when the extrusion blow molding process starts, air is introduced at the bottom of the die to expand the extruded blend and form a bubble. In addition, during the extrusion blow molding process, the blow-up ratio is controlled to be 2.7, the frost line height (distance from the die outlet) is 15 cm, the winding speed is 12.0 m / min, and the thickness of the film is about 6 - 10 μm.

[0058] The present invention uses a twin-screw extruder for extrusion granulation, and the set temperature of the twin-screw extruder is as follows:

[0059] Zone 1: 170 - 175 °C, Zone 2: 170 - 175 °C, Zone 3: 180 - 185 °C, Zone 4: 185 - 190 °C, Zone 5: 185 - 190 °C, Zone 6: 185 - 190 °C, Zone 7: 185 - 190 °C, Zone 8: 185 - 190 °C, Head: 180 - 190 °C, Screw rotation speed: 200 - 210 rpm.

[0060] The present invention uses a film blowing machine for blow molding, and the set temperature of the film blowing machine is as follows:

[0061] Zone 1: 170 - 180 °C, Zone 2: 180 - 185 °C, Zone 3: 185 - 190 °C, Zone 4: 185 - 190 °C, Head: 180 - 185 °C, Screw rotation speed: 40 - 45 rpm.

[0062] The present invention provides an application of the transparent polylactic acid film material with antibacterial, anti-ultraviolet aging, and high toughness described in the above technical solution in medical waste packaging bags, food wrap, food packaging, agricultural mulch films, or inner liners of trash cans.

[0063] To further illustrate the present invention, the following examples are used to describe in detail a transparent polylactic acid film with antibacterial, anti-ultraviolet aging, and high toughness, its preparation method, and its application provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0064] The raw materials used in the following cases are:

[0065] Polylactic acid, model REVODE110, Zhejiang Hisun Biomaterials Co., Ltd.;

[0066] Butyl acrylate (BA), Specification: GC, >99.0%, Tokyo Chemical Industry Co., Ltd.;

[0067] Methyl methacrylate (MMA), Specification: GC, >99.8%, Tokyo Chemical Industry Co., Ltd.;

[0068] Triallyl isocyanurate (TAIC), Specification: GC, >96.0%, Tokyo Chemical Industry Co., Ltd.;

[0069] 2,2,6,6 - Tetramethyl - 4 - piperidyl methacrylate (TMPMA), Specification: GC, >96.0%, Tokyo Chemical Industry Co., Ltd.;

[0070] Sodium dodecyl sulfate, Specification: ACS, ≥99.0%, Aladdin Reagent Co., Ltd.;

[0071] Potassium persulfate, Specification: ACS, ≥99.0%, Aladdin Reagent Co., Ltd.;

[0072] Anhydrous sodium carbonate, Specification: AR, Sinopharm Chemical Reagent Co., Ltd.;

[0073] Anhydrous magnesium sulfate, Specification: AR, Sinopharm Chemical Reagent Co., Ltd.;

[0074] Erucamide (EA), Xingbeida Chemical Materials Co., Ltd.;

[0075] Ethylene bisstearamide (EBS), Xingbeida Chemical Materials Co., Ltd.;

[0076] Tris(2,4 - di - tert - butylphenyl) phosphite, 168, Nanjing Hualiming Chemical Co., Ltd.;

[0077] Pentaerythritol tetrakis[(3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate], 1010, Nanjing Hualiming Chemical Co., Ltd.

[0078]

[0079] Example 1

[0080] Synthesis of poly(butyl acrylate) (PBA) emulsion

[0081] Design and synthesis of PBA emulsion. The synthesis process is as follows: Add 1 g of sodium dodecyl sulfate (SDS), 0.3 g of sodium carbonate, and 600 g of deionized water into a 2 L four-necked flask, stir mechanically (rotation speed 180 - 190 r / min), heat in a water bath to 75 °C, and simultaneously introduce argon gas. After introducing argon gas for 20 min, add 4 g of triallyl isocyanurate (TAIC) and 50 g of BA. After waiting for 30 min, add 30 g of an aqueous solution of potassium persulfate (KPS) (1%), and after the solution turns blue, continue the reaction for 20 min. Then, a mixed solution containing 125 g of BA, 4 g of TAIC, 1 g of SDS, and 40 g of H2O that has been fully pre-emulsified is added dropwise (dropwise speed 0.8 rpm) into the four-necked flask using a peristaltic pump. Every 1 h, add a supplementary amount of the KPS aqueous solution (30 g, 1%). After the mixed solution is added dropwise, continue the reaction for 2 h for curing. After the reaction ends, the solid content of the emulsion is measured by the weighing method to be 13.1%.

[0082] Synthesis of poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate (P(TMPMA-co-MMA)@PBA) emulsion

[0083] Design and synthesis of P(TMPMA-CO-MMA)@PBA emulsion. The synthesis process is as follows: Place a four-necked flask containing 200 g of PBA emulsion in a water bath, heat up to 75 °C, and continuously introduce argon gas. After introducing argon gas for 20 min, add 20 g of an aqueous solution of KPS (2%). Add 6 g of methyl methacrylate (MMA) and 2 g of 2,2,6,6-tetramethyl-4-piperidyl methacrylate (TMPMA) monomers into a single-necked flask, mix evenly, and then add dropwise (dropwise speed 0.4 rpm) into the four-necked flask using a peristaltic pump. After the addition is complete, continue the reaction for 2 h for curing. After the reaction ends, determine the solid content of the emulsion by weighing (16.3%).

[0084] Post-treatment of P(TMPMA-co-MMA)@PBA emulsion: Prepare 1 L of an aqueous solution of magnesium sulfate with a concentration of 0.5%, heat to 65 °C, and then pour the P(TMPMA-co-MMA)@PBA emulsion into the magnesium sulfate aqueous solution while stirring. Filter the precipitated polymer particles with a filter cloth, wash them repeatedly 3 times with water, and then place them in a vacuum drying oven at 50 °C for drying for 24 h to obtain P(TMPMA-co-MMA)@PBA.

[0085] Figure 1 Schematic diagram of the core-shell structure of P(TMPMA-co-MMA)@PBA, where PBA is the core and P(TMPMA-co-MMA) is the shell.

[0086] Figure 2Particle size distribution diagrams of PBA nanospheres and P(TMPMA-co-MMA)@PBA nanospheres, from Figure 2 it can be seen that: the average particle size of PBA nanospheres is about 100±5 nm, and the polydispersity index (PDI) of the particle size of the PBA emulsion is 0.069; the particle size of P(TMPMA-co-MMA)@PBA nanospheres is 140±7 nm, and the PDI of the particle size of the P(TMPMA-co-MMA)@PBA emulsion is 0.095. The increase in the particle size of the nanospheres is due to the successful grafting of the "shell" layer of P(TMPMA-co-MMA) onto the "core" of PBA.

[0087] Figure 3 is the transmission electron microscopy image of PBA nanospheres; Figure 4 is the transmission electron microscopy image of P(TMPMA-co-MMA)@PBA nanospheres; Figure 3 and Figure 4 it can be seen that: PBA nanospheres are spherical in shape, with uniform size, about 75±3 nm; P(TMPMA-co-MMA)@PBA nanospheres have an obvious "core-shell" structure, with uniform size, and the size of the nanospheres is 110±5 nm. It shows that P(TMPMA-co-MMA)@PBA nanospheres with a "core-shell" structure have been successfully prepared by emulsion polymerization.

[0088] Weigh 83.8 parts of PLA, 15 parts of P(TMPMA-co-MMA)@PBA, 0.5 part of EA, 0.5 part of EBS, 0.1 part of antioxidant 168, and 0.1 part of antioxidant 1010;

[0089] After mixing the (P(TMPMA-co-MMA)@PBA) nanospheres synthesized by the above method with PLA, lubricants (EA, EBS), and antioxidants (168, 1010) evenly, they are melt-blended and extruded through a twin-screw extruder to obtain a special resin of PLA / P(TMPMA-co-MMA)@PBA. Then, the special resin of PLA / P(TMPMA-co-MMA)@PBA is added to an extrusion blow molding machine for blow molding.

[0090] The set temperature of the twin-screw extruder is:

[0091] Zone 1: 170 - 175 °C, Zone 2: 170 - 175 °C, Zone 3: 180 - 185 °C, Zone 4: 185 - 190 °C, Zone 5: 185 - 190 °C, Zone 6: 185 - 190 °C, Zone 7: 185 - 190 °C, Zone 8: 185 - 190 °C, Head: 180 - 190 °C, Screw speed: 200 - 210 rpm.

[0092] The set temperature of the extrusion blow molding machine is:

[0093] Zone 1: 170 - 180 °C, Zone 2: 180 - 185 °C, Zone 3: 185 - 190 °C, Zone 4: 185 - 190 °C, Head: 180 - 185 °C, Screw speed: 40 - 45 rpm.

[0094] Example 2

[0095] Weigh PLA: 88.8 parts, P(TMPMA-co-MMA)@PBA: 10 parts, EA: 0.5 parts, EBS: 0.5 parts, Antioxidant 168: 0.1 part and Antioxidant 1010: 0.1 part;

[0096] The (P(TMPMA-co-MMA)@PBA) nanospheres synthesized by the experimental method in Example 1 were mixed evenly with PLA, lubricants (EA, EBS) and antioxidants (168, 1010), and then melt-blended and extruded through a twin-screw extruder to obtain a special resin of PLA / P(TMPMA-co-MMA)@PBA. Then the special resin of PLA / P(TMPMA-co-MMA)@PBA was added to an extrusion blow molding machine for blow molding.

[0097] The set temperature of the twin-screw extruder is:

[0098] Zone 1: 170 - 175 °C, Zone 2: 170 - 175 °C, Zone 3: 180 - 185 °C, Zone 4: 185 - 190 °C, Zone 5: 185 - 190 °C, Zone 6: 185 - 190 °C, Zone 7: 185 - 190 °C, Zone 8: 185 - 190 °C, Head: 180 - 190 °C, Screw speed: 200 - 210 rpm.

[0099] The set temperature of the extrusion blow molding machine is:

[0100] Zone 1: 170 - 180 °C, Zone 2: 180 - 185 °C, Zone 3: 185 - 190 °C, Zone 4: 185 - 190 °C, Head: 180 - 185 °C, Screw speed: 40 - 45 rpm.

[0101] Example 3

[0102] Weigh PLA: 77.6 parts, P(TMPMA-co-MMA)@PBA: 20 parts, EA: 1.0 part, EBS: 1.0 part, Antioxidant 168: 0.2 part and Antioxidant 1010: 0.2 part;

[0103] (P(TMPMA-co-MMA)@PBA) nanospheres synthesized by the experimental method in Example 1 were mixed evenly with PLA, lubricants (EA, EBS) and antioxidants (168, 1010), and then melt-blended and extruded through a twin-screw extruder to obtain a special resin of PLA / P(TMPMA-co-MMA)@PBA. Then, the special resin of PLA / P(TMPMA-co-MMA)@PBA was added to an extrusion blow molding machine for blow molding.

[0104] The set temperatures of the twin-screw extruder were as follows:

[0105] Zone 1: 170 - 175 °C, Zone 2: 170 - 175 °C, Zone 3: 180 - 185 °C, Zone 4: 185 - 190 °C, Zone 5: 185 - 190 °C, Zone 6: 185 - 190 °C, Zone 7: 185 - 190 °C, Zone 8: 185 - 190 °C, Head: 180 - 190 °C, Screw speed: 200 - 210 rpm.

[0106] The set temperatures of the extrusion blow molding machine were as follows:

[0107] Zone 1: 170 - 180 °C, Zone 2: 180 - 185 °C, Zone 3: 185 - 190 °C, Zone 4: 185 - 190 °C, Head: 180 - 185 °C, Screw speed: 40 - 45 rpm.

[0108] Example 4

[0109] 1. Synthesis of poly(n-butyl acrylate) (PBA) emulsion

[0110] A PBA emulsion was designed and synthesized as follows: 1 g of sodium dodecyl sulfate (SDS), 0.3 g of sodium carbonate and 600 g of deionized water were added to a 2 L four-necked flask, and mechanically stirred (rotation speed 180 - 190 r / min), heated to 75 °C in a water bath, and argon was introduced at the same time. After introducing argon for 20 min, 4 g of triallyl isocyanurate (TAIC) and 50 g of BA were added. After waiting for 30 min, 30 g of an aqueous solution of potassium persulfate (KPS) (1%) was added. After the solution turned blue, the reaction continued for 20 min. Then, a mixed solution containing 125 g of BA, 4 g of TAIC, 1 g of SDS, and 40 g of H2O that had been fully pre-emulsified was added dropwise (dropwise speed 0.8 rpm) to the four-necked flask using a peristaltic pump. Every 1 h, an aqueous solution of KPS (30 g, 1%) was added as a supplement. After the mixed solution was added dropwise, the reaction continued for 2 h for curing. After the reaction ended, the solid content of the emulsion was measured by the gravimetric method to be 13.1%.

[0111] 2. Synthesis of Poly(methacrylic acid 2,2,6,6 - tetramethyl - 4 - piperidyl ester - co - methyl methacrylate)@Poly(butyl acrylate) (P(TMPMA - co - MMA)@PBA) Emulsion

[0112] The synthesis process of P(TMPMA - CO - MMA)@PBA emulsion is as follows: Place a four - necked flask containing 200 g of PBA emulsion in a water bath, heat it to 75 °C, and continuously introduce argon gas. After introducing argon gas for 20 min, add 20 g of KPS aqueous solution (2%). Add 12 g of methyl methacrylate (MMA) and 4 g of methacrylic acid 2,2,6,6 - tetramethyl - 4 - piperidyl ester (TMPMA) monomers into a single - necked flask, mix them evenly, and then use a peristaltic pump to drop - add (drop - adding rate 0.4 rpm) into the four - necked flask. After the dropping is completed, continue the reaction for 2 h for curing. After the reaction is completed, weigh to determine the solid content of the emulsion (18.2%).

[0113] Post - treatment of P(TMPMA - co - MMA)@PBA emulsion: Prepare 1 L of magnesium sulfate aqueous solution with a concentration of 0.5%, heat it to 65 °C, and then pour the P(TMPMA - co - MMA)@PBA emulsion into the magnesium sulfate aqueous solution while stirring. Filter the precipitated polymer particles with a filter cloth, wash them repeatedly with water 3 times, and then place them in a vacuum drying oven at 50 °C for drying for 24 h.

[0114] Weigh 83.8 parts of PLA, 15 parts of P(TMPMA - co - MMA)@PBA, 0.5 part of EA, 0.5 part of EBS, 0.1 part of antioxidant 168, and 0.1 part of antioxidant 1010;

[0115] Mix the (P(TMPMA - co - MMA)@PBA) nanospheres synthesized by the above experimental method with PLA, lubricants (EA, EBS), and antioxidants (168, 1010) evenly, and then conduct melt - blending extrusion through a twin - screw extruder to obtain a special resin of PLA / P(TMPMA - co - MMA)@PBA. Then add the PLA / P(TMPMA - co - MMA)@PBA special resin into an extrusion blow - molding machine for blow - molding.

[0116] The set temperature of the twin - screw extruder is as follows:

[0117] Zone 1: 170 - 175 °C, Zone 2: 170 - 175 °C, Zone 3: 180 - 185 °C, Zone 4: 185 - 190 °C, Zone 5: 185 - 190 °C, Zone 6: 185 - 190 °C, Zone 7: 185 - 190 °C, Zone 8: 185 - 190 °C, Die head: 180 - 190 °C, Screw speed: 200 - 210 rpm.

[0118] The set temperature of the extrusion blow - molding machine is as follows:

[0119] Zone 1: 170 - 180 °C, Zone 2: 180 - 185 °C, Zone 3: 185 - 190 °C, Zone 4: 185 - 190 °C, Head: 180 - 185 °C, Screw speed: 40 - 45 rpm.

[0120] Example 5

[0121] 1. Synthesis of poly(butyl acrylate) (PBA) emulsion

[0122] The synthesis process of PBA emulsion is as follows: Add 1 g of sodium dodecyl sulfate (SDS), 0.3 g of sodium carbonate, and 600 g of deionized water into a 2 L four-necked flask, stir mechanically (rotation speed 180 - 190 r / min), heat in a water bath to 75 °C, and simultaneously introduce argon gas. After introducing argon gas for 20 min, add 4 g of triallyl isocyanurate (TAIC) and 50 g of BA. After waiting for 30 min, add 30 g of an aqueous potassium persulfate (KPS) solution (1%), and after the solution turns blue, continue the reaction for 20 min. Then, a mixed solution containing 125 g of BA, 4 g of TAIC, 1 g of SDS, and 40 g of H2O that has been fully pre-emulsified is added dropwise (dropwise speed 0.8 rpm) into the four-necked flask using a peristaltic pump. Every 1 h, add a supplementary amount of KPS aqueous solution (30 g, 1%). After the addition of the mixed solution is complete, continue the reaction for 2 h for curing. After the reaction is completed, the solid content of the emulsion is measured by the gravimetric method to be 13.1%.

[0123] 2. Synthesis of poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@poly(butyl acrylate) (P(TMPMA-co-MMA)@PBA) emulsion

[0124] Place a four-necked flask containing 200 g of PBA emulsion in a water bath, heat up to 75 °C, and continuously introduce argon gas. After introducing argon gas for 20 min, add 20 g of an aqueous KPS solution (2%). Add 18 g of methyl methacrylate (MMA) and 6 g of 2,2,6,6-tetramethyl-4-piperidyl methacrylate (TMPMA) monomers into a single-necked flask, mix evenly, and then add dropwise (dropwise speed 0.4 rpm) into the four-necked flask using a peristaltic pump. After the addition is complete, continue the reaction for 2 h for curing. After the reaction is completed, determine the solid content of the emulsion by weighing (20.4%).

[0125] Post-treatment of P(TMPMA-co-MMA)@PBA emulsion: Prepare 1 L of an aqueous magnesium sulfate solution with a concentration of 0.5%, heat it to 65 °C, and then pour the P(TMPMA-co-MMA)@PBA emulsion into the aqueous magnesium sulfate solution while stirring. Filter the precipitated polymer particles with a filter cloth, wash them repeatedly 3 times with water, and then place them in a vacuum drying oven at 50 °C for drying for 24 h.

[0126] Weigh 83.8 parts of PLA, 15 parts of P(TMPMA-co-MMA)@PBA, 0.5 part of EA, 0.5 part of EBS, 0.1 part of antioxidant 168, and 0.1 part of antioxidant 1010;

[0127] After mixing the (P(TMPMA-co-MMA)@PBA) nanospheres synthesized by the above experimental method with PLA, lubricants (EA, EBS), and antioxidants (168, 1010) uniformly, melt blending and extruding through a twin-screw extruder to obtain a special resin of PLA / P(TMPMA-co-MMA)@PBA. Then add the PLA / P(TMPMA-co-MMA)@PBA special resin into an extrusion blow molding machine for blow molding.

[0128] The set temperature of the twin-screw extruder is:

[0129] Zone 1: 170 - 175 °C, Zone 2: 170 - 175 °C, Zone 3: 180 - 185 °C, Zone 4: 185 - 190 °C, Zone 5: 185 - 190 °C, Zone 6: 185 - 190 °C, Zone 7: 185 - 190 °C, Zone 8: 185 - 190 °C, Head: 180 - 190 °C, Screw speed: 200 - 210 rpm.

[0130] The set temperature of the extrusion blow molding machine is:

[0131] Zone 1: 170 - 180 °C, Zone 2: 180 - 185 °C, Zone 3: 185 - 190 °C, Zone 4: 185 - 190 °C, Head: 180 - 185 °C, Screw speed: 40 - 45 rpm.

[0132] Comparative example

[0133] Weigh 97.8 parts of PLA, 1 part of EA, 1 part of EBS, 0.1 part of antioxidant 168, and 0.1 part of antioxidant 1010;

[0134] According to the above ratio, after uniformly mixing the dried polylactic acid with lubricants (EA, EBS) and antioxidants (168, 1010), melt blending and extruding through a twin-screw extruder to obtain a special resin for PLA blown film.

[0135] The set temperature of the twin-screw extruder is: Zone 1: 170 - 175 °C, Zone 2: 170 - 175 °C, Zone 3: 180 - 185 °C, Zone 4: 185 - 190 °C, Zone 5: 185 - 190 °C, Zone 6: 185 - 190 °C, Zone 7: 185 - 190 °C, Zone 8: 185 - 190 °C, Head: 180 - 190 °C, Screw speed: 200 - 210 rpm.

[0136] Then, the special resin for PLA blown film is added to an extrusion blow molding machine for blow molding to obtain a PLA film.

[0137] The set temperatures of the extrusion blow molding machine are as follows:

[0138] Zone 1: 170 - 180 °C, Zone 2: 180 - 185 °C, Zone 3: 185 - 190 °C, Zone 4: 185 - 190 °C, Die head: 180 - 185 °C, Screw speed: 40 - 45 rpm.

[0139] In the present invention, the blown film is cut into dumbbell-shaped samples (slightly different for different film thicknesses) (W×L = 4 mm×20 mm), and samples are taken along the longitudinal (MD) and transverse (TD) directions respectively. According to the standard ASTM D638-2008, a tensile testing machine is used to measure at a tensile speed of 20 mm / min. Each sample is measured at least 5 times, and the results are averaged. All tests are carried out at 23 °C and 50.0% relative humidity. The test results are listed in Table 1:

[0140] Table 1

[0141]

[0142] Table 2

[0143]

[0144] As can be seen from the above examples, the present invention provides a transparent polylactic acid film with antibacterial, anti-ultraviolet aging and high toughness. By weight, it comprises the following raw materials: 80 - 99 parts of polylactic acid, 1 - 20 parts of poly(methyl acrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres, 0.5 - 2 parts of lubricant and 0.2 - 0.4 parts of antioxidant. By adopting poly(methyl acrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres, the polylactic acid film has high toughness, and also has antibacterial, anti-ultraviolet aging and high transparency. The experimental results show that: the longitudinal Young's modulus of the transparent polylactic acid film is 1164 - 1763 MPa, the transverse Young's modulus is 986 - 1493 MPa, the longitudinal tensile strength is 32.8 - 62.3 MPa, and the transverse tensile strength is 23.9 - 56.5 MPa; the longitudinal elongation at break is 35.6% - 159.4%, and the transverse elongation at break is 36.2% - 167.8%; the transparency is 91.7 - 93.9%; the antibacterial rate is 97.4% - 99.8% (Escherichia coli) and 97.8% - 99.9% (Staphylococcus aureus), and the anti-ultraviolet aging rate is 84.4 - 91.2% (tensile strength retention rate) and 83.3 - 91.5% (elongation at break retention rate).

[0145] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A transparent polylactic acid film with antibacterial, anti-ultraviolet aging and high toughness, comprising the following raw materials by weight parts: 80-99 parts of polylactic acid, 1-20 parts of poly(methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres, 0.5-2 parts of lubricant and 0.2-0.4 parts of antioxidant.

2. The transparent polylactic acid film according to claim 1, wherein The poly(methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres have a polybutyl acrylate core and a copolymer of methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester and methyl methacrylate as the shell.

3. The transparent polylactic acid film according to claim 1, wherein The poly(methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres are prepared by the following method: Heat the polybutyl acrylate emulsion to 70-80 °C, remove oxygen, add a radical initiator, and then dropwise add a mixed solution of methyl methacrylate and methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester, and cure to obtain a cured product; Add the cured product to a demulsifier, precipitate the polymer, filter, wash with water, and dry to obtain poly(methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres.

4. The transparent polylactic acid film according to claim 3, wherein The mass ratio of polybutyl acrylate, methyl methacrylate and methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester in the polybutyl acrylate emulsion is (100-110):(3-3.3):(1-1.1).

5. The transparent polylactic acid film according to claim 3, wherein The curing temperature is 70-75 °C, and the curing time is 110-130 min.

6. The transparent polylactic acid film according to claim 3, characterized in that, The radical initiator is selected from an aqueous solution of potassium persulfate or an aqueous solution of ammonium persulfate; The demulsifier is selected from an aqueous solution of magnesium sulfate, an aqueous solution of sodium chloride or an aqueous solution of aluminum sulfate.

7. The transparent polylactic acid film according to claim 1, wherein The lubricant is selected from erucamide and ethylene bisstearamide; The antioxidant is selected from tris(2,4-di-tert-butylphenyl) phosphite and pentaerythritol tetrakis[(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

8. The transparent polylactic acid film according to claim 7, characterized in that, The transparent polylactic acid film material comprises the following raw materials: 80-99 parts of polylactic acid, 1-20 parts of poly(methyl methacrylate-2,2,6,6-tetramethyl-4-piperidyl ester-co-methyl methacrylate)@polybutyl acrylate nanospheres, 0.5-1.0 part of erucamide, 0.5-1.0 part of ethylene bisstearamide, 0.1-0.2 part of tris(2,4-di-tert-butylphenyl) phosphite and 0.1-0.2 part of pentaerythritol tetrakis[(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

9. A method for preparing the transparent polylactic acid film with antibacterial, anti-ultraviolet aging and high toughness according to claim 1, comprising the following steps: After uniformly mixing polylactic acid, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-methyl methacrylate)@polybutyl acrylate nanospheres, a lubricant, and an antioxidant, extrusion granulation is carried out, followed by blow molding to obtain a transparent polylactic acid film with antibacterial, anti-ultraviolet aging, and high toughness.

10. Use of the transparent polylactic acid film with antibacterial, anti-ultraviolet aging, and high toughness according to any one of claims 1 to 8 in medical waste packaging bags, food wrap, food packaging, agricultural mulch films, or inner lining films for trash cans.

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