Degradable PS film and preparation method thereof

Abstract

The invention discloses a degradable PS film and a preparation method thereof, and relates to the technical field of high polymer material processing. The material is prepared from the following raw materials in parts by mass: 50 to 60 parts of recycled polystyrene resin, 20 to 30 parts of polycaprolactone-b-polystyrene copolymer, 8 to 10 parts of PBAT resin, 3 to 5 parts of compatilizer, 3 to 5 parts of nano zinc oxide, 0.8 to 1.2 parts of coupling agent, 2 to 3 parts of auxiliary agent, 1 to 3 parts of amphoteric salt and 3 to 5 parts of reactive beta-cyclodextrin quaternary ammonium salt. The degradable PS film not only can meet the optical performance requirement, but also has good degradation performance.

Description

Technical Field

[0001] This invention relates to the field of polymer material processing technology, and in particular to a biodegradable PS film and its preparation method. Background Technology

[0002] Polystyrene (PS), a widely used thermoplastic, holds a significant market share in packaging, food containers, and other fields due to its excellent transparency, processability, and low cost. However, traditional PS materials are difficult to degrade naturally, resulting in long-term environmental pollution after disposal. With increasingly stringent environmental regulations, the development of biodegradable PS materials has become an urgent need. Existing degradation technologies are mainly divided into photodegradation, biodegradation, and composite degradation, but they generally suffer from low degradation efficiency or significant loss of mechanical properties. In particular, when materials need to simultaneously meet the optical performance requirements of high light transmittance and low haze, it is often difficult to balance degradation performance.

[0003] For example, patent document CN110951176B discloses a biodegradable polystyrene resin and its preparation method. This material is prepared from the following components in parts by weight: 60-80 parts polystyrene, 5-10 parts surface-treated lignin fibers, 10-20 parts polylactic acid, 5-10 parts compatibilizer, and 0.5 parts antioxidant. The biodegradable polystyrene resin prepared by this invention introduces two biodegradable components, surface-treated lignin fibers and polylactic acid, into the polystyrene matrix, enabling the final matrix material to partially degrade, thus reducing pollution caused by the large-scale application of this type of material. The surface treatment method for the lignin fibers used in this invention can effectively improve the compatibility between the lignin fibers and the matrix material. Compared with traditional fillers (talc, calcium carbonate, mica, etc.), the material density of this invention is significantly lower than that of products using traditional fillers while achieving the same material performance. However, the light transmittance of this material decreases significantly, and the haze is relatively large, which cannot meet the light transmittance requirements of high-end packaging. In addition, uneven melting is prone to occur during processing, affecting the molding quality.

[0004] It is evident that developing a PS film material that can meet both optical performance requirements and has good degradation properties has become an important research direction in the current plastics industry. Summary of the Invention

[0005] The main objective of this invention is to overcome the aforementioned shortcomings and provide a biodegradable PS film and its preparation method. This film uses PS as a base material, and through the synergistic effect of other raw materials and interfacial modification by a compatibilizer, combined with an optimized biaxial stretching process, achieves a balance between low haze and excellent biodegradability, while also possessing good mechanical properties, meeting the requirements of high-end packaging and other fields.

[0006] To achieve the above objectives, the present invention provides a biodegradable PS film, which, by mass parts, comprises the following raw materials: 50-60 parts recycled polystyrene resin, 20-30 parts polycaprolactone-b-polystyrene copolymer, 8-10 parts PBAT resin, 3-5 parts compatibilizer, 3-5 parts nano zinc oxide, 0.8-1.2 parts coupling agent, 2-3 parts additives, 1-3 parts amphoteric salt, and 3-5 parts reactive β-cyclodextrin quaternary ammonium salt.

[0007] Preferably, the recycled polystyrene resin is recycled GPPS 666D-AMST.

[0008] Preferably, the M of the polycaprolactone-b-polystyrene copolymer n =9600g / mol, PD=1.41, of which caprolactone content is 60%.

[0009] Preferably, the PBAT resin is PBAT A400.

[0010] Preferably, the compatibilizer is a styrene-maleic anhydride copolymer with a maleic anhydride content of 18% and a grade of KS-01.

[0011] Preferably, the average particle size of the nano-zinc oxide is 10-50 nm.

[0012] Preferably, the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570.

[0013] Preferably, the additives are antioxidants, plasticizers, and slip agents compounded in a mass ratio of 1:(1-2):(0.5-0.8).

[0014] Preferably, the antioxidant is antioxidant 1010; the plasticizer is triethyl citrate; and the slip agent is stearamide.

[0015] Preferably, the amphoteric salt is at least one of 2-aminoethylphosphonic acid and glycine betaine.

[0016] Preferably, the reactive β-cyclodextrin quaternary ammonium salt is prepared according to the method in Example 5 of CN106008755B.

[0017] Another object of the present invention is to provide a method for preparing the biodegradable PS film, comprising the following steps: Step S1: Mix the raw materials, except for the reactive β-cyclodextrin quaternary ammonium salt, according to the weight parts to obtain a mixture; add the mixture to a twin-screw extruder for extrusion, and the melt is cast through a coat hanger die to a 60°C mirror roller to obtain a 450μm thick casting sheet; Step S2: The casting sheet is biaxially stretched, heat-set, and then cooled to 60°C to obtain the primary film; Step S3: Irradiate the nascent membrane under electron beam radiation and store it at low temperature after irradiation; mix reactive β-cyclodextrin quaternary ammonium salt, Tween 20 and water, stir for 30 minutes under nitrogen atmosphere, and then quickly add the irradiated membrane. React at 60°C in a water bath for 4-6 hours. After the membrane is taken out, wash it repeatedly with deionized water and ethanol, and dry it to obtain a biodegradable PS membrane.

[0018] Preferably, the extrusion temperature in step S1 is 180–210°C, the twin-screw extruder speed is 350–650 rpm, the pressure is 2–3 MPa, and the length-to-diameter ratio of the twin-screw extruder is (39–45):1.

[0019] Preferably, in step S2, the longitudinal stretching temperature is 100-110℃ and the stretching ratio is 3-4 times; the transverse stretching temperature is 100-110℃ and the stretching ratio is 3-4 times.

[0020] Preferably, the heat setting temperature in step S2 is 120-130℃, and the time is 5-10s.

[0021] Preferably, the dose of electron beam radiation in step S3 is 50-150 kGy.

[0022] Preferably, the mass ratio of β-cyclodextrin quaternary ammonium salt, Tween 20, and water in step S3 is 10:1:60.

[0023] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The biodegradable PS film disclosed in this invention comprises, by mass parts, 50-60 parts of recycled polystyrene resin, 20-30 parts of polycaprolactone-b-polystyrene copolymer, 8-10 parts of PBAT resin, 3-5 parts of compatibilizer, 3-5 parts of nano zinc oxide, 0.8-1.2 parts of coupling agent, 2-3 parts of additive, 1-3 parts of amphoteric salt, and 3-5 parts of reactive β-cyclodextrin quaternary ammonium salt. Through the synergistic effect of the various raw materials, the film can meet the optical performance requirements and has good degradation performance.

[0024] (2) The biodegradable PS film disclosed in this invention is constructed by precisely compounding polycaprolactone-b-polystyrene copolymer with PBAT resin A400, utilizing the block structure of the copolymer to build a “recycled PS-copolymer-PBAT” compatible network, and combining electron beam radiation to initiate the grafting of reactive β-cyclodextrin quaternary ammonium salt to form crosslinking points, which not only enhances the intermolecular forces but also provides degradation active sites, giving the product the advantages of high degradation rate and mechanical properties.

[0025] (3) The biodegradable PS film disclosed in this invention uses recycled GPPS 666D-AMST as the substrate and is combined with a compatibilizer KS-01 containing 18% maleic anhydride. Through the interaction between the anhydride groups of the compatibilizer and the end groups of recycled PS and polycaprolactone-b-PS copolymer, the interfacial bonding force is significantly improved. At the same time, the process matching of twin-screw extrusion (180-210℃, 350-650rpm) and coat hanger die casting ensures the uniform dispersion of a high proportion of recycled material. Compared with the existing low-proportion recycling system, this technology has low raw material costs and high film forming rate, achieving a dual improvement in environmental protection and economy.

[0026] (4) The biodegradable PS film disclosed in this invention uses amphoteric salts to enhance the compatibility of multiple components and regulate the suitable microenvironment for microorganisms through dual active sites. The reactive β-cyclodextrin quaternary ammonium salt achieves long-term function and cross-linking regulation through electron beam grafting. The two work together to solve the problem of difficult degradation of recycled PS by improving hydrophilicity, providing enzyme recognition sites and constructing degradation channels. Furthermore, by matching refractive index, inhibiting component aggregation and regulating crystallinity, the film still maintains good optical performance after the addition of multiple functional components, thus achieving complementary advantages and synergistic optimization of degradation performance and transparency.

[0027] (5) The biodegradable PS film disclosed in this invention has nano zinc oxide that can synergize with other raw materials through mechanisms such as “providing microbial attachment sites, regulating material surface charge, promoting enzyme catalysis, and photocatalysis” to improve degradation performance; at the same time, its addition can improve mechanical properties without affecting optical performance. Detailed Implementation

[0028] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. Example 1

[0029] A biodegradable PS film, by mass parts, comprises the following raw materials: 50 parts recycled polystyrene resin, 20 parts polycaprolactone-b-polystyrene copolymer, 8 parts PBAT resin, 3 parts compatibilizer, 3 parts nano zinc oxide, 0.8 parts coupling agent, 2 parts additives, 1 part amphoteric salt, and 3 parts reactive β-cyclodextrin quaternary ammonium salt.

[0030] The recycled polystyrene resin is recycled GPPS 666D-AMST; the M of the polycaprolactone-b-polystyrene copolymer n=9600g / mol, PD=1.41, wherein the caprolactone content is 60%; the PBAT resin is PBAT A400; the compatibilizer is styrene-maleic anhydride copolymer, the maleic anhydride content is 18%, and the grade is KS-01; the average particle size of the nano zinc oxide is 10nm; the coupling agent is silane coupling agent KH550; the additives are antioxidants, plasticizers, and slip agents compounded in a mass ratio of 1:1:0.5; the antioxidant is antioxidant 1010; the plasticizer is triethyl citrate; the slip agent is stearamide; the amphoteric salt is 2-aminoethylphosphonic acid; the reactive β-cyclodextrin quaternary ammonium salt is prepared according to the method in Example 5 of CN106008755B.

[0031] A method for preparing the biodegradable PS film includes the following steps: Step S1: Mix the raw materials, except for the reactive β-cyclodextrin quaternary ammonium salt, according to the weight parts to obtain a mixture; add the mixture to a twin-screw extruder for extrusion, and the melt is cast through a coat hanger die to a 60°C mirror roller to obtain a 450μm thick casting sheet; Step S2: The casting sheet is biaxially stretched, heat-set, and then cooled to 60°C to obtain the primary film; Step S3: Irradiate the nascent membrane under electron beam radiation and store it at low temperature after irradiation; mix reactive β-cyclodextrin quaternary ammonium salt, Tween 20 and water, stir for 30 minutes under nitrogen atmosphere, and then quickly add the irradiated membrane. React at 60°C in a water bath for 4 hours. After the membrane is taken out, wash it repeatedly with deionized water and ethanol, and dry it to obtain a biodegradable PS membrane.

[0032] In step S1, the extrusion temperature is 180℃, the twin-screw extruder speed is 350rpm, the pressure is 2MPa, and the length-to-diameter ratio of the twin-screw extruder is 39:1; in step S2, the longitudinal stretching temperature is 100℃, and the stretching ratio is 3 times; the transverse stretching temperature is 100℃, and the stretching ratio is 3 times; in step S2, the heat setting temperature is 120℃, and the time is 5s; in step S3, the electron beam radiation dose is 50kGy; and in step S3, the mass ratio of β-cyclodextrin quaternary ammonium salt, Tween 20, and water is 10:1:60. Example 2

[0033] A biodegradable PS film, by mass parts, comprises the following raw materials: 53 parts recycled polystyrene resin, 23 parts polycaprolactone-b-polystyrene copolymer, 8.5 parts PBAT resin, 3.5 parts compatibilizer, 3.5 parts nano zinc oxide, 0.9 parts coupling agent, 2.3 parts additives, 1.5 parts amphoteric salt, and 3.5 parts reactive β-cyclodextrin quaternary ammonium salt.

[0034] The recycled polystyrene resin is recycled GPPS 666D-AMST; the M of the polycaprolactone-b-polystyrene copolymer n =9600g / mol, PD=1.41, wherein the caprolactone content is 60%; the PBAT resin is PBAT A400; the compatibilizer is styrene-maleic anhydride copolymer, the maleic anhydride content is 18%, and the grade is KS-01; the average particle size of the nano zinc oxide is 20nm; the coupling agent is silane coupling agent KH560; the additives are antioxidants, plasticizers, and slip agents compounded in a mass ratio of 1:1.3:0.6; the antioxidant is antioxidant 1010; the plasticizer is triethyl citrate; the slip agent is stearamide; the amphoteric salt is glycine betaine; the reactive β-cyclodextrin quaternary ammonium salt is prepared according to the method in Example 5 of CN106008755B.

[0035] A method for preparing the biodegradable PS film includes the following steps: Step S1: Mix the raw materials, except for the reactive β-cyclodextrin quaternary ammonium salt, according to the weight parts to obtain a mixture; add the mixture to a twin-screw extruder for extrusion, and the melt is cast through a coat hanger die to a 60°C mirror roller to obtain a 450μm thick casting sheet; Step S2: The casting sheet is biaxially stretched, heat-set, and then cooled to 60°C to obtain the primary film; Step S3: Irradiate the nascent membrane under electron beam radiation and store it at low temperature after irradiation; mix reactive β-cyclodextrin quaternary ammonium salt, Tween 20 and water, stir for 30 minutes under nitrogen atmosphere, and then quickly add the irradiated membrane. React at 60°C in a water bath for 4.5 hours. After the membrane is taken out, wash it repeatedly with deionized water and ethanol, and dry it to obtain a biodegradable PS membrane.

[0036] In step S1, the extrusion temperature is 190℃, the twin-screw extruder speed is 450rpm, the pressure is 2.3MPa, and the length-to-diameter ratio of the twin-screw extruder is 41:1; in step S2, the longitudinal stretching temperature in the biaxial stretching is 103℃, and the stretching ratio is 3.3 times; the transverse stretching temperature is 103℃, and the stretching ratio is 3.3 times; in step S2, the heat setting temperature is 123℃, and the time is 6s; in step S3, the electron beam radiation dose is 80kGy; and in step S3, the mass ratio of β-cyclodextrin quaternary ammonium salt, Tween 20, and water is 10:1:60. Example 3

[0037] A biodegradable PS film, by mass parts, comprises the following raw materials: 55 parts recycled polystyrene resin, 25 parts polycaprolactone-b-polystyrene copolymer, 9 parts PBAT resin, 4 parts compatibilizer, 4 parts nano zinc oxide, 1 part coupling agent, 2.5 parts additives, 2 parts amphoteric salt, and 4 parts reactive β-cyclodextrin quaternary ammonium salt.

[0038] The recycled polystyrene resin is recycled GPPS 666D-AMST; the M of the polycaprolactone-b-polystyrene copolymer n =9600g / mol, PD=1.41, wherein the caprolactone content is 60%; the PBAT resin is PBAT A400; the compatibilizer is styrene-maleic anhydride copolymer, the maleic anhydride content is 18%, and the grade is KS-01; the average particle size of the nano zinc oxide is 30nm; the coupling agent is silane coupling agent KH570; the additives are antioxidants, plasticizers, and slip agents compounded in a mass ratio of 1:1.5:0.65; the antioxidant is antioxidant 1010; the plasticizer is triethyl citrate; the slip agent is stearamide; the amphoteric salt is 2-aminoethylphosphonic acid; the reactive β-cyclodextrin quaternary ammonium salt is prepared according to the method in Example 5 of CN106008755B.

[0039] A method for preparing the biodegradable PS film includes the following steps: Step S1: Mix the raw materials, except for the reactive β-cyclodextrin quaternary ammonium salt, according to the weight parts to obtain a mixture; add the mixture to a twin-screw extruder for extrusion, and the melt is cast through a coat hanger die to a 60°C mirror roller to obtain a 450μm thick casting sheet; Step S2: The casting sheet is biaxially stretched, heat-set, and then cooled to 60°C to obtain the primary film; Step S3: Irradiate the nascent membrane under electron beam radiation and store it at low temperature after irradiation; mix reactive β-cyclodextrin quaternary ammonium salt, Tween 20 and water, stir for 30 minutes under nitrogen atmosphere, and then quickly add the irradiated membrane. React at 60°C in a water bath for 4-6 hours. After the membrane is taken out, wash it repeatedly with deionized water and ethanol, and dry it to obtain a biodegradable PS membrane.

[0040] In step S1, the extrusion temperature is 195℃, the twin-screw extruder speed is 500 rpm, the pressure is 2.5 MPa, and the length-to-diameter ratio of the twin-screw extruder is 42:1; in step S2, the longitudinal stretching temperature is 105℃, and the stretching ratio is 3.5 times; the transverse stretching temperature is 105℃, and the stretching ratio is 3.5 times; in step S2, the heat setting temperature is 125℃, and the time is 7.5 s; in step S3, the electron beam radiation dose is 100 kGy; and in step S3, the mass ratio of β-cyclodextrin quaternary ammonium salt, Tween 20, and water is 10:1:60. Example 4

[0041] A biodegradable PS film, by mass parts, comprises the following raw materials: 58 parts recycled polystyrene resin, 28 parts polycaprolactone-b-polystyrene copolymer, 9.5 parts PBAT resin, 4.5 parts compatibilizer, 4.5 parts nano zinc oxide, 1.1 parts coupling agent, 2.8 parts additives, 2.5 parts amphoteric salt, and 4.5 parts reactive β-cyclodextrin quaternary ammonium salt.

[0042] The recycled polystyrene resin is recycled GPPS 666D-AMST; the M of the polycaprolactone-b-polystyrene copolymer n =9600g / mol, PD=1.41, wherein the caprolactone content is 60%; the PBAT resin is PBAT A400; the compatibilizer is a styrene-maleic anhydride copolymer with a maleic anhydride content of 18% and a grade of KS-01; the average particle size of the nano zinc oxide is 40 nm; the coupling agent is a compound of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570 in a mass ratio of 1:2:1; the additives are an antioxidant, plasticizer, and slip agent compounded in a mass ratio of 1:1.8:0.75; the antioxidant is antioxidant 1010; the plasticizer is triethyl citrate; the slip agent is stearamide; the amphoteric salt is a compound of 2-aminoethylphosphonic acid and glycine betaine in a mass ratio of 3:5; the reactive β-cyclodextrin quaternary ammonium salt is prepared according to the method in Example 5 of CN106008755B.

[0043] A method for preparing the biodegradable PS film includes the following steps: Step S1: Mix the raw materials, except for the reactive β-cyclodextrin quaternary ammonium salt, according to the weight parts to obtain a mixture; add the mixture to a twin-screw extruder for extrusion, and the melt is cast through a coat hanger die to a 60°C mirror roller to obtain a 450μm thick casting sheet; Step S2: The casting sheet is biaxially stretched, heat-set, and then cooled to 60°C to obtain the primary film; Step S3: Irradiate the nascent membrane under electron beam radiation and store it at low temperature after irradiation; mix reactive β-cyclodextrin quaternary ammonium salt, Tween 20 and water, stir for 30 minutes under nitrogen atmosphere, and then quickly add the irradiated membrane. React at 60°C in a water bath for 5.5 hours. After the membrane is taken out, wash it repeatedly with deionized water and ethanol, and dry it to obtain a biodegradable PS membrane.

[0044] In step S1, the extrusion temperature is 205℃, the twin-screw extruder speed is 600rpm, the pressure is 2.8MPa, and the length-to-diameter ratio of the twin-screw extruder is 44:1; in step S2, the longitudinal stretching temperature in the biaxial stretching is 108℃, and the stretching ratio is 3.8 times; the transverse stretching temperature is 108℃, and the stretching ratio is 3.8 times; in step S2, the heat setting temperature is 128℃, and the time is 9s; in step S3, the electron beam radiation dose is 140kGy; and in step S3, the mass ratio of β-cyclodextrin quaternary ammonium salt, Tween 20, and water is 10:1:60. Example 5

[0045] A biodegradable PS film, by mass parts, comprises the following raw materials: 60 parts recycled polystyrene resin, 30 parts polycaprolactone-b-polystyrene copolymer, 10 parts PBAT resin, 5 parts compatibilizer, 5 parts nano zinc oxide, 1.2 parts coupling agent, 3 parts additives, 3 parts amphoteric salt, and 5 parts reactive β-cyclodextrin quaternary ammonium salt.

[0046] The recycled polystyrene resin is recycled GPPS 666D-AMST; the M of the polycaprolactone-b-polystyrene copolymer n =9600g / mol, PD=1.41, wherein the caprolactone content is 60%; the PBAT resin is PBAT A400; the compatibilizer is styrene-maleic anhydride copolymer, the maleic anhydride content is 18%, and the grade is KS-01; the average particle size of the nano zinc oxide is 50nm; the coupling agent is silane coupling agent KH550; the additives are antioxidants, plasticizers, and slip agents compounded in a mass ratio of 1:2:0.8; the antioxidant is antioxidant 1010; the plasticizer is triethyl citrate; the slip agent is stearamide; the amphoteric salt is 2-aminoethylphosphonic acid; the reactive β-cyclodextrin quaternary ammonium salt is prepared according to the method in Example 5 of CN106008755B.

[0047] A method for preparing the biodegradable PS film includes the following steps: Step S1: Mix the raw materials, except for the reactive β-cyclodextrin quaternary ammonium salt, according to the weight parts to obtain a mixture; add the mixture to a twin-screw extruder for extrusion, and the melt is cast through a coat hanger die to a 60°C mirror roller to obtain a 450μm thick casting sheet; Step S2: The casting sheet is biaxially stretched, heat-set, and then cooled to 60°C to obtain the primary film; Step S3: Irradiate the nascent membrane under electron beam radiation and store it at low temperature after irradiation; mix reactive β-cyclodextrin quaternary ammonium salt, Tween 20 and water, stir for 30 minutes under nitrogen atmosphere, and then quickly add the irradiated membrane. React at 60°C in a water bath for 4-6 hours. After the membrane is taken out, wash it repeatedly with deionized water and ethanol, and dry it to obtain a biodegradable PS membrane.

[0048] In step S1, the extrusion temperature is 210℃, the twin-screw extruder speed is 650rpm, the pressure is 3MPa, and the length-to-diameter ratio of the twin-screw extruder is 45:1; in step S2, the longitudinal stretching temperature is 110℃, and the stretching ratio is 4 times; the transverse stretching temperature is 110℃, and the stretching ratio is 4 times; in step S2, the heat setting temperature is 130℃, and the time is 10s; in step S3, the electron beam radiation dose is 150kGy; and in step S3, the mass ratio of β-cyclodextrin quaternary ammonium salt, Tween 20, and water is 10:1:60.

[0049] Comparative Example 1 A biodegradable PS film and its preparation method are basically the same as those in Example 5, except that an equal amount of polycaprolactone-b-polystyrene copolymer is used instead of PBAT resin.

[0050] Comparative Example 2 A biodegradable PS film and its preparation method are basically the same as those in Example 5, except that an equal amount of PBAT resin is used instead of polycaprolactone-b-polystyrene copolymer.

[0051] Comparative Example 3 A biodegradable PS film and its preparation method are basically the same as those in Example 5, except that no amphoteric salt is added.

[0052] Comparative Example 4 A biodegradable PS film and its preparation method are basically the same as those in Example 5, except that no reactive β-cyclodextrin quaternary ammonium salt is added.

[0053] Comparative Example 5 A biodegradable PS film and its preparation method are basically the same as those in Example 5, except that no nano zinc oxide is added.

[0054] To further illustrate the beneficial technical effects of the biodegradable PS films involved in the various embodiments of the present invention, relevant performance tests were conducted on the biodegradable PS films involved in Example 5 and Comparative Examples 1-5. The test results are shown in Table 1, and the test methods are as follows: (1) Haze: The test was conducted in accordance with GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics". Each sample was tested 3 times and the average value was taken. (2) Degradation performance: Referring to GB / T 19277.1-2011 "Determination of final aerobic biodegradation capacity of materials under controlled composting conditions - Part 1: General method", a soil degradation test was conducted. The film sample (size 20mm×20mm×50μm, weight about 0.5g) was buried in natural soil at 25℃ and 60% humidity at a depth of 20cm. Samples were taken periodically, and the degradation rate was calculated using the weight loss method. The test time was 1000h.

[0055] (3) Mechanical properties: The tensile strength was tested in accordance with GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets" using an electronic universal testing machine. The tensile speed was 50 mm / min, the sample type was type 2, and 5 samples were tested for each sample. The average value was taken.

[0056] Table 1. Test results of antibacterial PS film performance project Haze Tensile strength 1000h degradation rate unit % MPa % Example 5 1.2 40.5 26.9 Comparative Example 1 3.8 32.0 12.0 Comparative Example 2 3.1 38.5 20.5 Comparative Example 3 2.8 36.0 18.0 Comparative Example 4 2.0 39.2 15.3 Comparative Example 5 2.3 37.3 22.1 As can be seen from Table 1, the optical, mechanical and degradable properties of the biodegradable PS film of Example 5 are significantly better than those of the comparative example. The combined use of polycaprolactone-b-polystyrene copolymer, PBAT resin, amphoteric salt, reactive β-cyclodextrin quaternary ammonium salt and nano zinc oxide is beneficial to improving the above properties.

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A biodegradable PS film, characterized in that, By mass, its raw material composition includes: 50-60 parts recycled polystyrene resin, 20-30 parts polycaprolactone-b-polystyrene copolymer, 8-10 parts PBAT resin, 3-5 parts compatibilizer, 3-5 parts nano zinc oxide, 0.8-1.2 parts coupling agent, 2-3 parts additives, 1-3 parts amphoteric salt, and 3-5 parts reactive β-cyclodextrin quaternary ammonium salt.

2. The biodegradable PS film according to claim 1, characterized in that, The recycled polystyrene resin is recycled GPPS 666D-AMST; the M of the polycaprolactone-b-polystyrene copolymer n =9600g / mol, PD=1.41, of which caprolactone content is 60%.

3. The biodegradable PS film according to claim 1, characterized in that, The PBAT resin is PBAT A400; the compatibilizer is a styrene-maleic anhydride copolymer with a maleic anhydride content of 18% and a grade of KS-01.

4. The biodegradable PS film according to claim 1, characterized in that, The average particle size of the nano zinc oxide is 10-50 nm; the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570.

5. The biodegradable PS film according to claim 1, characterized in that, The additives are antioxidants, plasticizers, and slip agents compounded in a mass ratio of 1:(1-2):(0.5-0.8); the antioxidant is antioxidant 1010; the plasticizer is triethyl citrate; and the slip agent is stearamide.

6. The biodegradable PS film according to claim 1, characterized in that, The amphoteric salt is at least one of 2-aminoethylphosphonic acid and glycine betaine.

7. A method for preparing a biodegradable PS film according to any one of claims 1-6, characterized in that, Includes the following steps: Step S1: Mix the raw materials, except for the reactive β-cyclodextrin quaternary ammonium salt, according to the weight parts to obtain a mixture; add the mixture to a twin-screw extruder for extrusion, and the melt is cast through a coat hanger die to a 60°C mirror roller to obtain a 450μm thick casting sheet; Step S2: The casting sheet is biaxially stretched, heat-set, and then cooled to 60°C to obtain the primary film; Step S3: Irradiate the nascent membrane under electron beam radiation and store it at low temperature after irradiation; mix reactive β-cyclodextrin quaternary ammonium salt, Tween 20 and water, stir for 30 minutes under nitrogen atmosphere, and then quickly add the irradiated membrane. React at 60°C in a water bath for 4-6 hours. After the membrane is taken out, wash it repeatedly with deionized water and ethanol, and dry it to obtain a biodegradable PS membrane.

8. The method for preparing the biodegradable PS film according to claim 7, characterized in that, The extrusion temperature in step S1 is 180-210℃, the twin-screw extruder speed is 350-650 rpm, the pressure is 2-3 MPa, and the length-to-diameter ratio of the twin-screw extruder is (39-45):

1.

9. The method for preparing the biodegradable PS film according to claim 7, characterized in that, In step S2, the longitudinal stretching temperature is 100-110℃ and the stretching ratio is 3-4 times; the transverse stretching temperature is 100-110℃ and the stretching ratio is 3-4 times; the heat setting temperature in step S2 is 120-130℃ and the time is 5-10s.

10. The method for preparing the biodegradable PS film according to claim 7, characterized in that, The dose of electron beam radiation in step S3 is 50-150 kGy; the mass ratio of β-cyclodextrin quaternary ammonium salt, Tween 20, and water in step S3 is 10:1:60.