Antibacterial regenerated plastic and production process thereof

Abstract

The invention discloses antibacterial regenerated plastic and a production process thereof, and belongs to the technical field of plastic recycling. The antibacterial regenerated plastic is prepared from, by mass, 80-100 parts of PP recycled materials, 5-15 parts of compatilizer, 6-18 parts of skin-core fibers, 8-24 parts of vanillin and 2-5 parts of magnolol, the skin layer material of the skin-core fibers is polyvinyl alcohol-amino, and the core layer material of the skin-core fibers is chitosan. In the processing process, the PP recycled material and the compatilizer are added into a screw extruder from a main feed port, other components are added from a side feed port, and the antibacterial regenerated plastic is obtained through melt extrusion granulation. Natural antibacterial components vanillin and magnolol are added into the PP recycled material, skin-core fibers are synchronously added, polyvinyl alcohol-amino of a skin layer and chitosan of a core layer form composite fibers, and the regenerated plastic is endowed with efficient, broad-spectrum and long-acting antibacterial effects and excellent mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of plastic recycling technology, specifically relating to an antibacterial recycled plastic and its production process. Background Technology

[0002] Plastics are a key material for addressing the world's sustainability challenges. One way to reduce plastic waste is to increase circularity, creating a closed loop that allows materials to continue to function. In the field of plastic recycling and regeneration, different plastic materials possess varying recyclability. Some plastics, due to their chemical structure and physical properties, can be easily recycled and regenerated, while others may be difficult to recycle due to difficulties in separation or high recycling costs.

[0003] Polypropylene (PP) has advantages such as low cost, low density, easy processing, good chemical resistance, and excellent mechanical properties, making it the most commonly used thermoplastic polymer in daily life. Recycled polypropylene (PP) plastics have the highest recycling rate among plastics and are widely used in packaging materials, automotive parts, furniture, and even the construction industry.

[0004] In recent years, the requirements for the antibacterial properties of materials have gradually increased. The hydrophobicity and inertness of polypropylene surfaces often lead to bacterial contamination, hindering its potential application in the antibacterial field. Typically, the recycling method for PP recycled plastic involves collection and sorting followed by direct melt regeneration. However, general antibacterial components are difficult to withstand high-temperature pyrolysis, and the active components become ineffective during the melt regeneration process, making it difficult to achieve the desired antibacterial effect and thus hindering its potential application in the antibacterial field. Summary of the Invention

[0005] This invention provides an antibacterial recycled plastic and its production process, which can solve the problem of poor antibacterial properties of PP recycled plastic in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: An antibacterial recycled plastic, comprising the following raw materials by parts by weight: 80-100 parts recycled PP, 5-15 parts compatibilizer, 6-18 parts core and sheath fiber, 8-24 parts vanillin, and 2-5 parts magnolol.

[0007] The sheath material of the core-sheath fiber is polyvinyl alcohol-amino, and the core material is chitosan.

[0008] The mechanical properties of recycled PP generally decrease. Adding fiber materials to recycled PP can enhance these properties, while traditional fibers are all solid fibers. Core-sheath fibers are designed and prepared using different materials. The polyvinyl alcohol-amino layer in the sheath encapsulates the heat-sensitive chitosan, preventing direct and prolonged contact with the high-temperature melt during processing and preserving the antibacterial activity of chitosan. Vanillin and magnolol have different antibacterial mechanisms and can produce a synergistic effect, broadening the antibacterial spectrum and reducing the concentration of single antibacterial agents, thus improving efficiency. Simultaneously, the polyvinyl alcohol-amino layer can rapidly form products containing oxazine ring structures with vanillin and magnolol through the Mannich reaction. Oxazine compounds possess excellent antibacterial properties and, compared to direct natural antibacterial materials, have better temperature resistance, preventing the loss of antibacterial active components during the processing of recycled plastics.

[0009] Furthermore, the amino groups on the polyvinyl alcohol-amino layer in the sheath are key active groups. They can undergo hydrogen bonding with the chitosan in the core layer (which is itself rich in amino groups) and the added vanillin and magnolol (containing aldehyde and phenolic hydroxyl groups), and even possibly Schiff base reactions (amino and aldehyde groups), thus firmly "anchoring" the antibacterial agent to the fiber carrier and preventing its rapid migration and loss. When the polyvinyl alcohol-amino layer of the sheath fiber is partially melted and destroyed during processing, the exposed chitosan can synergistically fight bacteria with vanillin and magnolol.

[0010] Furthermore, the compatibilizer is maleic anhydride-grafted polypropylene.

[0011] Maleic anhydride-grafted polypropylene, as a compatibilizer, improves the interfacial compatibility between hydrophobic recycled PP and relatively hydrophilic core-sheath fibers. The PP portion of its molecular chain is compatible with the recycled PP matrix, while the terminal anhydride groups can chemically react with the amino groups on the surface of the core-sheath fibers, enabling the fibers to be uniformly dispersed and firmly embedded in the matrix, thus ensuring the uniformity and durability of the product's mechanical properties and antibacterial effects.

[0012] Furthermore, the mass ratio of the core-sheath fiber, vanillin, and magnolol is (3-5):(4-6):1.

[0013] Furthermore, the core-sheath fiber is prepared as follows: Polyvinyl alcohol-amino spinning solution and chitosan spinning solution were prepared. Chitosan spinning solution was used as the core layer and polyvinyl alcohol-amino spinning solution was used as the sheath layer. Primary fibers were prepared by coaxial wet spinning process. Sheath-core fibers were obtained by coagulation bath, stretching, washing and drying processes.

[0014] Furthermore, the solvent of the polyvinyl alcohol-amino spinning solution is deionized water, the dissolution temperature of polyvinyl alcohol-amino is 80-90℃, and the concentration of polyvinyl alcohol-amino in the spinning solution is 15-20wt%.

[0015] Furthermore, the solvent of the chitosan spinning solution is an aqueous acetic acid solution, wherein the volume fraction of acetic acid in the aqueous acetic acid solution is 1-5%, and the concentration of chitosan in the chitosan spinning solution is 3-6 wt%.

[0016] Furthermore, in the coaxial wet spinning process, the ratio of the extrusion velocity of the sheath layer to the extrusion velocity of the core layer is 1.5:1.0-1.2.

[0017] Furthermore, the coagulation bath is a mixed aqueous solution of sodium sulfate and sodium hydroxide; The concentration of sodium hydroxide in the mixed aqueous solution is 5-8 wt%; The concentration of sodium sulfate in the mixed aqueous solution is 10-15 wt%.

[0018] A process for producing antibacterial recycled plastics includes the following steps: Step 1: Prepare the raw materials according to the proportions. Put the recycled PP material and compatibilizer into a high-speed mixer and mix evenly to obtain a mixture. Step 2: The mixture is fed into the screw extruder through the main feed port. After passing through the conveying section and the melting section, a melt is formed in the screw extruder. The core fiber, vanillin, and magnolol are conveyed into the rear of the melting section through the side feed port. The material in the screw extruder enters the mixing section, the venting section, and the homogenizing section. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0019] In the screw extrusion granulation process, recycled PP and compatibilizer are added at the main feed inlet, undergoing a complete melting process. A side-feed method is used, adding core-sheath fibers and natural antibacterial agents from the rear of the melting section, shortening their residence time in the high-temperature melt and minimizing thermal decomposition and failure. Since the plastic is completely melted at the rear of the melting section, adding functional components at this point, under the shear force of the subsequent mixing section, is sufficient to break up the fibers and distribute them evenly in the matrix, without damaging the fiber structure due to excessive shearing.

[0020] Furthermore, the temperature of the conveying section is 170-180℃, the temperature of the melting section is 200-210℃, the temperature of the mixing section is 205-215℃, the temperature of the exhaust section is 200-210℃, the temperature of the homogenization section is 190-200℃, and the screw speed is 50-80 rpm.

[0021] The beneficial effects of this invention are: (1) Add natural antibacterial components vanillin and magnolol to PP recycled material, and simultaneously add core fiber. Polyvinyl alcohol-amino in the outer layer and chitosan in the core layer form composite fiber, giving the recycled plastic an efficient, broad-spectrum and long-lasting antibacterial effect and improving mechanical properties.

[0022] (2) The core fiber is protected by the polyvinyl alcohol-amino of the outer layer against the chitosan of the core layer, which avoids thermal decomposition failure during the processing of recycled plastics. The amino group contained in the polyvinyl alcohol-amino participates in the Mannich reaction and reacts with vanillin and magnolol to form high-temperature resistant oxazine compounds, which have long-lasting antibacterial properties.

[0023] (3) Vanillin and magnolol in recycled plastics can exert antibacterial effects independently, and can also be loaded and bound to the core fiber through chemical reaction to form a unified and functional new antibacterial additive. The stable chemical structure greatly reduces the risk of failure of antibacterial active components.

[0024] (4) Chitosan in the core layer of the sheath-core fiber is a natural material and a powerful natural antibacterial agent. Together with the added vanillin and magnolol, it forms a multi-mechanism, synergistic antibacterial system. Even if the polyvinyl alcohol-amino protective structure of the sheath is partially damaged during processing, the chitosan in the core layer can still form hydrogen bonds with other components in the recycled plastic using amino groups, thus ensuring stability while exerting antibacterial effects.

[0025] (5) In the processing and preparation of recycled plastics, the compatibility between the core fiber and the PP matrix is ​​improved by side feeding and the use of compatibilizer, which ensures the feasibility of production and the mechanical properties of the final product.

[0026] (6) This invention upgrades low-value PP recycled material into high-value-added recycled plastic with long-lasting antibacterial function, which can be widely used in food packaging, medical and health care, daily household, automotive interior and other fields, with broad market prospects. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] Preparation of core-sheath fibers: Step 1: Prepare polyvinyl alcohol-amino spinning solution and chitosan spinning solution Polyvinyl alcohol-amino was added to deionized water and heated to 85°C with constant stirring to dissolve, forming a polyvinyl alcohol-amino spinning solution with a concentration of 16wt%.

[0030] Acetic acid and deionized water are mixed to form an acetic acid aqueous solution with a volume fraction of 3%. Chitosan is weighed and added to the acetic acid aqueous solution and stirred to dissolve to form a chitosan spinning solution. The concentration of chitosan is controlled at 5 wt%.

[0031] Step 2: Prepare the coagulation bath

[0032] Sodium hydroxide was added to deionized water and stirred to dissolve, forming a 5 wt% sodium hydroxide solution. Sodium sulfate was then added and stirred to dissolve, forming a mixed aqueous solution with a sodium sulfate concentration of 12 wt%.

[0033] Step 3: Using the chitosan spinning solution prepared in Step 1 as the core layer and the polyvinyl alcohol-amino spinning solution as the sheath layer, nascent fibers are prepared using a coaxial wet spinning process. The external needle is 18G (Φ0.84×1.28mm) and the internal needle is 25G (Φ0.26×0.52mm). The sheath extrusion flow rate is 200uL / min, and the core extrusion flow rate is 140uL / min. The mixed aqueous solution prepared in Step 2 is added to the coagulation bath, and the temperature of the coagulation bath is set to 30℃. The nascent fibers enter the coagulation bath and gradually coagulate. They are then drawn by a drawing roller with a drawing ratio of 2. After drawing, they are washed in a water washing tank and then dried. After drying, the sheath-core fibers are obtained. The sheath-core fibers are cut into short fibers for later use.

[0034] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride grafted polypropylene, 9 parts core-sheath fiber, 12 parts vanillin, and 3 parts magnolol. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0035] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0036] Example 2

[0037] The only difference from Example 1 is that the mass fraction of vanillin in the raw material of antibacterial recycled plastic is adjusted to 15 parts, while the other steps and conditions are the same as in Example 1.

[0038] Example 3

[0039] The only difference from Example 1 is that the mass fraction of vanillin in the raw material of antibacterial recycled plastic is adjusted to 18 parts, while the other steps and conditions are the same as in Example 1.

[0040] Example 4

[0041] The only difference from Example 3 is that the mass fraction of core-sheath fibers in the raw materials for antibacterial recycled plastic is adjusted to 12 parts. The steps and conditions for preparing the core-sheath fibers are the same as in Example 1.

[0042] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride grafted polypropylene, 12 parts core-sheath fiber, 18 parts vanillin, and 3 parts magnolol. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0043] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0044] Example 5

[0045] The only difference from Example 3 is that the mass fraction of core-sheath fibers in the raw materials for antibacterial recycled plastic is adjusted to 15 parts. The steps and conditions for preparing the core-sheath fibers are the same as in Example 1.

[0046] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride grafted polypropylene, 15 parts core-sheath fiber, 18 parts vanillin, and 3 parts magnolol. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0047] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0048] Example 6

[0049] The only difference from Example 4 is that the raw materials for the antibacterial recycled plastic contain 16 parts core-sheath fiber, 24 parts vanillin, and 4 parts magnolol. The steps and conditions for preparing the core-sheath fiber are the same as in Example 1.

[0050] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride grafted polypropylene, 16 parts core-sheath fiber, 24 parts vanillin, and 4 parts magnolol. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0051] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0052] Example 7

[0053] The only difference from Example 4 is that the raw materials for the antibacterial recycled plastic contain 8 parts core-sheath fiber, 12 parts vanillin, and 2 parts magnolol. The steps and conditions for preparing the core-sheath fiber are the same as in Example 1.

[0054] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride grafted polypropylene, 8 parts core-sheath fiber, 12 parts vanillin, and 2 parts magnolol. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0055] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0056] Example 8

[0057] The only difference from Example 5 is that the mass fraction of maleic anhydride-grafted polypropylene in the raw materials of the antibacterial recycled plastic is adjusted to 12 parts, and the steps and conditions for preparing the core-sheath fiber are the same as in Example 1.

[0058] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 12 parts maleic anhydride-grafted polypropylene, 15 parts core-sheath fiber, 18 parts vanillin, and 3 parts magnolol. Put the recycled PP and maleic anhydride-grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0059] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0060] Example 9

[0061] The only difference from Example 5 is that the mass fraction of maleic anhydride-grafted polypropylene in the raw materials of the antibacterial recycled plastic is adjusted to 15 parts, and the steps and conditions for preparing the core-sheath fiber are the same as in Example 1.

[0062] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 15 parts maleic anhydride grafted polypropylene, 15 parts core-sheath fiber, 18 parts vanillin, and 3 parts magnolol. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0063] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0064] Comparative Example 1

[0065] The only difference from Example 1 is that solid fibers prepared with polyvinyl alcohol-amino are used to replace the core-sheath fibers.

[0066] Preparation of polyvinyl alcohol-amino fiber: Step 1: Prepare polyvinyl alcohol-amino spinning solution Polyvinyl alcohol-amino was added to deionized water and heated to 85°C with constant stirring to dissolve, forming a polyvinyl alcohol-amino spinning solution with a concentration of 16wt%.

[0067] Step 2: Prepare the coagulation bath

[0068] Sodium sulfate is added to deionized water and stirred to dissolve, forming a saturated sodium sulfate solution.

[0069] Step 3: The polyvinyl alcohol-amino spinning solution prepared in Step 1 is added to the wet spinning equipment. The extrusion flow rate is 200 μL / min. The nascent fibers are formed by extrusion through the spinneret. The saturated sodium sulfate solution prepared in Step 2 is added to the coagulation bath. The temperature of the coagulation bath is set to 30°C. The nascent fibers enter the coagulation bath and gradually coagulate. They are then drawn by the drawing rollers at a drawing ratio of 2. After drawing, they are washed in the washing tank and then dried. After drying, polyvinyl alcohol-amino fibers are obtained, which are then cut into short fibers for later use.

[0070] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride grafted polypropylene, 9 parts core-sheath fiber, 12 parts vanillin, and 3 parts magnolol. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix evenly to obtain a mixture.

[0071] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers, vanillin, and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0072] Comparative Example 2

[0073] The only difference from Example 1 is that the antibacterial recycled plastic does not contain core-sheath fibers in its raw materials.

[0074] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride-grafted polypropylene, 12 parts vanillin, and 3 parts magnolol. Put the recycled PP and maleic anhydride-grafted polypropylene into a high-speed mixer and mix them evenly to obtain a mixture.

[0075] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. Vanillin and magnolol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0076] Comparative Example 3

[0077] The only difference from Example 1 is that vanillin is not added to the raw materials of the antibacterial recycled plastic.

[0078] The steps and conditions for preparing the core-sheath fiber are the same as in Example 1.

[0079] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride-grafted polypropylene, 9 parts core-sheath fiber, and 3 parts magnolol. Put the recycled PP and maleic anhydride-grafted polypropylene into a high-speed mixer and mix them evenly to obtain a mixture.

[0080] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers and honokiol are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0081] Comparative Example 4

[0082] The only difference from Example 1 is that magnolol is not added to the raw materials of the antibacterial recycled plastic.

[0083] The steps and conditions for preparing the core-sheath fiber are the same as in Example 1.

[0084] Preparation of antibacterial recycled plastics: Step 1: Prepare the raw materials according to the following proportions: 90 parts recycled PP, 10 parts maleic anhydride grafted polypropylene, 9 parts core-sheath fiber, and 12 parts vanillin. Put the recycled PP and maleic anhydride grafted polypropylene into a high-speed mixer and mix them evenly to obtain a mixture.

[0085] Step 2: Set the five temperature zones of the screw extruder: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. Set the screw speed to 60 rpm. Feed the mixture into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The core and sheath fibers and vanillin are conveyed into the rear of the melting section through the side feeder. The material in the screw extruder enters the mixing, venting, and homogenization sections. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

[0086] Comparative Example 5

[0087] The only difference from Example 1 is that recycled PP material is directly remelted and granulated to produce recycled plastic.

[0088] Preparation of recycled plastics: The screw extruder is set to five temperature zones: 180℃ for the conveying section, 210℃ for the melting section, 215℃ for the mixing section, 210℃ for the venting section, and 200℃ for the homogenization section. The screw speed is set to 60 rpm. Recycled PP material is fed into the screw extruder through the main feed inlet. After passing through the conveying and melting sections, a melt is formed in the screw extruder. The melt then enters the mixing, venting, and homogenization sections. After extrusion, the material is cooled and granulated to obtain recycled plastic.

[0089] The performance of the recycled plastics prepared in Examples 1-9 and Comparative Examples 1-5 was tested, and the results are shown in Table 1.

[0090] The recycled plastic was pressed into strips (50mm×125mm×4mm) using a tablet press and then subjected to tensile strength testing, referring to the standard GB / T 1040.1-2006.

[0091] Antibacterial properties are tested according to the antibacterial test standard QB / T2591. The assay was performed according to 2003A, and the bacteria used for testing were Staphylococcus aureus, Escherichia coli, and Aspergillus niger.

[0092] Table 1

[0093] As shown in Table 1, among Examples 1-3, the antibacterial recycled plastic prepared in Example 2 exhibits the best antibacterial performance, indicating that the amount of vanillin added is most suitable. In Example 3, excessive vanillin was added. Given the limited amount of phenol and core-sheath fibers in the raw materials, the excess aldehyde leads to the direct combination of amino groups with aldehyde groups to form a cross-linked structure, occupying reaction sites and making it difficult to form oxazine compounds, thus reducing antibacterial performance. Furthermore, the excess aldehyde will thermally decompose to form small molecules, weakening the mechanical properties of the material. To address the issue of excessive aldehyde addition in Example 3, the proportion of core-sheath fibers was appropriately increased. In Example 4, more amino groups were able to react with phenol and aldehyde to form oxazine compounds, resulting in improved antibacterial and mechanical properties compared to Example 3. With the same amount of compatibilizer added, the compatibility between the excess core-sheath fibers and the matrix decreased in Example 5, leading to a reduction in overall performance. While maintaining the ratio of the main antibacterial components—core-sheath fibers, vanillin, and magnolol—in Examples 6 and 7, the proportions of the three components were kept constant, but the overall percentage of the three raw materials in the plastic was adjusted. Among Examples 4, 6, and 7, the antibacterial recycled plastic of Example 4 exhibits significantly better antibacterial performance. Example 5 was improved by adjusting the proportion of maleic anhydride-grafted polypropylene compatibilizer in the raw materials. The mechanical and antibacterial properties of Examples 8 and 9 were improved compared to Example 5. Combined with the test results of the comparative examples and Example 1, it can be seen that the components in the examples of this invention have a synergistic effect, which is crucial to the overall performance of the recycled plastics. The antibacterial and mechanical properties of the recycled plastics in the comparative examples are not as good as those in Example 1.

[0094] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An antibacterial recycled plastic, characterized in that, By weight, it includes the following raw materials: 80-100 parts recycled PP, 5-15 parts compatibilizer, 6-18 parts core-sheath fiber, 8-24 parts vanillin, and 2-5 parts magnolol; The sheath material of the core-sheath fiber is polyvinyl alcohol-amino, and the core material is chitosan.

2. The antibacterial recycled plastic according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene.

3. The antibacterial recycled plastic according to claim 1, characterized in that, The mass ratio of the core-sheath fiber, vanillin, and magnolol is (3-5):(4-6):

1.

4. The antibacterial recycled plastic according to claim 1, characterized in that, The core-sheath fiber is prepared as follows: Polyvinyl alcohol-amino spinning solution and chitosan spinning solution were prepared. Chitosan spinning solution was used as the core layer and polyvinyl alcohol-amino spinning solution was used as the sheath layer. Primary fibers were prepared by coaxial wet spinning process. Sheath-core fibers were obtained by coagulation bath, stretching, washing and drying processes.

5. The antibacterial recycled plastic according to claim 4, characterized in that, The solvent of the polyvinyl alcohol-amino spinning solution is deionized water, the dissolution temperature of polyvinyl alcohol-amino is 80-90℃, and the concentration of polyvinyl alcohol-amino in the spinning solution is 15-20wt%.

6. The antibacterial recycled plastic according to claim 4, characterized in that, The solvent of the chitosan spinning solution is an aqueous acetic acid solution, wherein the volume fraction of acetic acid in the aqueous acetic acid solution is 1-5%, and the concentration of chitosan in the chitosan spinning solution is 3-6 wt%.

7. The antibacterial recycled plastic according to claim 4, characterized in that, In the coaxial wet spinning process, the ratio of the extrusion flow rate of the sheath layer to the extrusion flow rate of the core layer is 1.5:1.0-1.

2.

8. The antibacterial recycled plastic according to claim 4, characterized in that, The coagulation bath is a mixed aqueous solution of sodium sulfate and sodium hydroxide; The concentration of sodium hydroxide in the mixed aqueous solution is 5-8 wt%; The concentration of sodium sulfate in the mixed aqueous solution is 10-15 wt%.

9. A production process for antibacterial recycled plastics as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Prepare the raw materials according to the proportions. Put the recycled PP material and compatibilizer into a high-speed mixer and mix evenly to obtain a mixture. Step 2: The mixture is fed into the screw extruder through the main feed port. After passing through the conveying section and the melting section, a melt is formed in the screw extruder. The core fiber, vanillin, and magnolol are conveyed into the rear of the melting section through the side feed port. The material in the screw extruder enters the mixing section, the venting section, and the homogenizing section. After extrusion, it is cooled and granulated to obtain antibacterial recycled plastic.

10. The production process of antibacterial recycled plastic according to claim 9, characterized in that, The temperature of the conveying section is 170-180℃, the temperature of the melting section is 200-210℃, the temperature of the mixing section is 205-215℃, the temperature of the exhaust section is 200-210℃, the temperature of the homogenization section is 190-200℃, and the screw speed is 50-80 rpm.

Images