Biodegradable plastic master batch and preparation method thereof

Abstract

The invention provides a biodegradable plastic master batch and a preparation method thereof, and belongs to the field of high polymer materials, the biodegradable plastic master batch comprises the following components: 100 parts of cellulose acetate grafted polylactic acid, 15-25 parts of polycaprolactone, 14-16 parts of carbon nanotube doped talcum powder, 3-7 parts of a plasticizer, 1-5 parts of a compatibilizer and 0.5-2 parts of a lubricant. According to the biodegradable plastic master batch and the preparation method thereof, the interface bonding strength between the talcum powder and the polylactic acid can be improved, meanwhile, the crystal nucleus generation capacity of the talcum powder is effectively improved, and the mechanical strength and heat resistance of the polylactic acid are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a biodegradable plastic masterbatch and its preparation method. Background Technology

[0002] Polylactic acid (PLA) is a polymer obtained by polymerizing lactic acid obtained through bio-fermentation. It is a completely degradable, non-toxic and harmless polymer with high strength, high modulus and good transparency. It has gradually become a potential alternative to petroleum-based polymers and is one of the most widely used green polymer materials.

[0003] Traditional PLA has poor heat resistance and its mechanical strength decreases significantly at high temperatures, which limits its application range to some extent. In order to improve the heat resistance of polylactic acid, existing technologies generally modify the crystallinity and orientation structure of polylactic acid by adding nucleating agents, or introduce rigid structural materials or highly crystalline materials through composite modification to enhance the heat resistance of polylactic acid.

[0004] Talc is a filler that serves to enhance mechanical strength and reduce costs. It also exhibits nucleation properties in polylactic acid (PLA). The lamellar structure of talc can act as heterogeneous nucleation sites, promoting the orderly arrangement and crystallization of PLA molecular chains. This can improve the crystallization conditions and properties of PLA to some extent, thereby increasing its heat distortion temperature. However, the interfacial bonding between talc and PLA is weak, and the layered structure of talc limits its dispersion and nucleation capabilities, thus limiting its ability to improve the heat resistance of PLA. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides a biodegradable plastic masterbatch and its preparation method, which can improve the interfacial bonding strength between talc and polylactic acid, while effectively improving the crystal nucleation ability of talc, thereby enhancing the mechanical strength of polylactic acid and effectively improving its heat resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A biodegradable plastic masterbatch, by weight, comprises the following components: 100 parts cellulose acetate-grafted polylactic acid, 15-25 parts polycaprolactone, 14-16 parts carbon nanotube-doped talc, 3-7 parts plasticizer, 1-5 parts compatibilizer, and 0.5-2 parts lubricant.

[0007] Furthermore, the method for preparing the cellulose acetate-grafted polylactic acid includes the following steps: A1. Dissolve cellulose acetate in a solvent, add bromoisobutyryl bromide and react to obtain bromoisobutyrylated cellulose acetate; A2. The catalyst is dispersed in lactic acid monomer to obtain a dispersion, and the dispersion is mixed with bromoisobutyrylated cellulose acetate to obtain a mixture; A3. The mixture from step A2 is subjected to a polymerization reaction. After the reaction is complete, cellulose acetate grafted polylactic acid is obtained.

[0008] Furthermore, in step A2, the mass ratio of lactic acid monomer to bromoisobutyrylated cellulose acetate is 10:1.1-1.3.

[0009] Furthermore, the preparation method of the carbon nanotube-doped talc powder includes the following steps: B1. Add talc powder to an alkaline solution, soak, filter, and calcine at high temperature to obtain pretreated talc powder; B2. The pretreated talc powder is placed in a carbon nanotube dispersion and rapidly cooled, then filtered and dried to obtain the carbon nanotube-doped talc powder.

[0010] Furthermore, the plasticizer is one or a mixture of two or more of glycerol, polyglycerol, and ethylene glycol.

[0011] Furthermore, the compatibilizer is one or a mixture of two or more of glycidyl methacrylate, L-lysine triisocyanate, and maleic anhydride-grafted ethylene-octene copolymer.

[0012] Furthermore, the lubricant is one or a mixture of calcium stearate and zinc stearate.

[0013] Furthermore, the particle size of the talc powder mentioned in step B1 satisfies: D95≤25μm.

[0014] A method for preparing biodegradable plastic masterbatch includes the following steps: S1. Grafting cellulose acetate onto polylactic acid, polycaprolactone, and carbon nanotubes doped with talc powder, and then melt-blending them in a twin-screw extruder, yields modified polylactic acid; S2. Modified polylactic acid is mixed evenly with the remaining raw materials, added to a twin-screw extruder for melt blending, and then extruded and granulated to obtain biodegradable plastic masterbatch.

[0015] Furthermore, the temperatures of each section of the extruder are as follows: temperature control zone 1 180±2℃, temperature control zone 2 185±2℃, temperature control zone 3 190±2℃, and die head temperature 185±2℃.

[0016] This application has the following beneficial effects: 1. Polycaprolactone can effectively improve the brittleness of polylactic acid and achieve reinforcement and toughness. This invention can effectively improve the thermodynamic compatibility of cellulose acetate grafted with polylactic acid and polycaprolactone by grafting cellulose acetate with polylactic acid, avoid the phase separation phenomenon that may occur after blending, and improve the mechanical strength and heat resistance of polylactic acid.

[0017] 2. This invention, through alkali treatment of talc powder, etches microcracks on the talc powder surface, exposing more active groups and enhancing its reactivity. High-temperature calcination causes the microcracks to expand, facilitating the infiltration of carbon nanotubes. Finally, rapid cooling of the carbon nanotube dispersion causes volume shrinkage, resulting in stable intercalations of carbon nanotubes at the microcrack sites of the talc powder. These intercalations are uniformly and firmly distributed on the talc powder surface. This not only reduces the hydrophilicity of talc powder and improves its interfacial compatibility with the non-polar polymer matrix, but also allows the carbon nanotubes to form uniformly distributed active sites on the talc powder surface, promoting rapid crystallization and forming a cross-linked network between polycaprolactone and cellulose acetate grafted polylactic acid, effectively improving the mechanical properties and heat resistance of the material. Detailed Implementation

[0018] The present application will be further described in detail below with reference to the embodiments.

[0019] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0020] Example 1 A biodegradable plastic masterbatch, by weight, comprises the following components: 100 parts cellulose acetate-grafted polylactic acid, 20 parts polycaprolactone, 15 parts carbon nanotube-doped talc, 5 parts plasticizer, 3 parts compatibilizer, and 1 part lubricant, wherein the talc particle size D95 = 20 μm, the plasticizer is glycerol, the compatibilizer is glycidyl methacrylate, and the lubricant is calcium stearate. The biodegradable plastic masterbatch is prepared by the following steps: S1. Add cellulose acetate-grafted polylactic acid, polycaprolactone, and carbon nanotube-doped talc powder to a twin-screw extruder for melt blending to obtain modified polylactic acid; S2. Mix the modified polylactic acid with the remaining raw materials evenly, add it to a twin-screw extruder for melt blending, extrusion granulation, and obtain biodegradable plastic masterbatch. The temperatures of each section of the extruder are as follows: temperature control zone 1 180±2℃, temperature control zone 2 185±2℃, temperature control zone 3 190±2℃, and die head temperature 185±2℃.

[0021] The preparation method of cellulose acetate grafted with polylactic acid includes the following steps: A1. Weigh 1 part of cellulose acetate by weight and add it to a mixed solution of 20 parts of tetrahydrofuran and 0.5 parts of pyridine. Stir until dissolved, then slowly add 0.8 parts of bromoisobutyryl bromide in an ice-water bath. After stirring and reacting at room temperature for 36 hours, precipitate, filter and dry the reaction mixture to obtain bromoisobutyrylated cellulose acetate. A2. Disperse 0.15 parts of zinc lactate catalyst in 10 parts of lactic acid monomer to obtain a dispersion, and mix the dispersion with 1.2 parts of bromoisobutyrylated cellulose acetate to obtain a mixture; A3. Place the mixture from step A2 into a reactor and carry out a polymerization reaction at a temperature of 130°C for 8 hours. After the reaction is complete, cellulose acetate grafted polylactic acid is obtained.

[0022] Furthermore, the preparation method of carbon nanotube-doped talc includes the following steps: B1. Add talc powder to a 0.5% sodium hydroxide solution, soak, filter, and calcine at a high temperature of 600-700℃ for 1-2 hours to obtain pretreated talc powder. B2. After removing the pretreated talc powder, quickly place it into a carbon nanotube dispersion with a mass concentration of 0.3% and N,N-dimethylformamide as the dispersing solvent for cooling. After filtration and drying, the carbon nanotube-doped talc powder is obtained.

[0023] Example 2 A biodegradable plastic masterbatch, by weight, comprises the following components: 100 parts cellulose acetate-grafted polylactic acid, 15 parts polycaprolactone, 14 parts carbon nanotube-doped talc, 3 parts plasticizer, 1 part compatibilizer, and 0.5 parts lubricant, wherein the talc particle size D95 = 20 μm, the plasticizer is polyglycerol, the compatibilizer is L-lysine triisocyanate, and the lubricant is zinc stearate. The biodegradable plastic masterbatch is prepared by the following steps: S1. After cellulose acetate-grafted polylactic acid is dried in a vacuum drying oven, cellulose acetate-grafted polylactic acid, polycaprolactone, and carbon nanotube-doped talc are added to a twin-screw extruder for melt blending to obtain modified polylactic acid. S2. Mix the modified polylactic acid with the remaining raw materials evenly, add it to a twin-screw extruder for melt blending, extrusion granulation, and obtain biodegradable plastic masterbatch. The temperatures of each section of the extruder are as follows: temperature control zone 1 178℃, temperature control zone 2 185℃, temperature control zone 3 190℃, and die head temperature 183℃.

[0024] The preparation method of cellulose acetate grafted with polylactic acid includes the following steps: A1. Weigh 1 part of cellulose acetate by weight and add it to a mixed solution of 20 parts of tetrahydrofuran and 0.3 parts of pyridine. Stir until dissolved, then slowly add 0.5 parts of bromoisobutyryl bromide in an ice-water bath. After stirring and reacting at room temperature for 24 hours, precipitate, filter and dry the reaction mixture to obtain bromoisobutyrylated cellulose acetate. A2. Disperse 0.1 parts of stannous octoate catalyst in 10 parts of lactic acid monomer to obtain a dispersion, and mix the dispersion with 1.1 parts of bromoisobutyrylated cellulose acetate to obtain a mixture; A3. Place the mixture from step A2 into a reactor and carry out a polymerization reaction at a temperature of 120°C for 12 hours. After the reaction is complete, cellulose acetate grafted polylactic acid is obtained.

[0025] A method for preparing carbon nanotube-doped talc includes the following steps: B1. Add talc powder to a 0.3% sodium hydroxide solution, soak, filter, and calcine at a high temperature of 600℃ for 2 hours to obtain pretreated talc powder. B2. After removing the pretreated talc powder, quickly place it into a carbon nanotube dispersion with a mass concentration of 0.1% and N,N-dimethylformamide as the dispersing solvent for cooling. After filtration and drying, the carbon nanotube-doped talc powder is obtained.

[0026] Example 3 A biodegradable plastic masterbatch, by weight, comprises the following components: 100 parts cellulose acetate-grafted polylactic acid, 25 parts polycaprolactone, 16 parts carbon nanotube-doped talc, 7 parts plasticizer, 5 parts compatibilizer, and 2 parts lubricant, wherein the talc particle size D95 = 20 μm, the plasticizer is ethylene glycol, the compatibilizer is maleic anhydride-grafted ethylene-octene copolymer, and the lubricant is calcium stearate. The biodegradable plastic masterbatch is prepared by the following steps: S1. After cellulose acetate-grafted polylactic acid is dried in a vacuum drying oven, cellulose acetate-grafted polylactic acid, polycaprolactone, and carbon nanotube-doped talc are added to a twin-screw extruder for melt blending to obtain modified polylactic acid. S2. Mix the modified polylactic acid with the remaining raw materials evenly, add it to a twin-screw extruder for melt blending, extrusion granulation, and obtain biodegradable plastic masterbatch. The temperatures of each section of the extruder are as follows: temperature control zone 1 180℃, temperature control zone 2 185℃, temperature control zone 3 190℃, and die head temperature 185℃.

[0027] The preparation method of cellulose acetate grafted with polylactic acid includes the following steps: A1. Weigh 1 part of cellulose acetate by weight and add it to a mixed solution of 20 parts of tetrahydrofuran and 1 part of pyridine. Stir until dissolved, then slowly add 1 part of bromoisobutyryl bromide dropwise under an ice-water bath. After stirring and reacting at room temperature for 48 hours, precipitate, filter and dry the reaction mixture to obtain bromoisobutyrylated cellulose acetate. A2. Disperse 0.2 parts of zinc lactate catalyst / stannous octoate catalyst in 10 parts of lactic acid monomer to obtain a dispersion, and mix the dispersion with 1.3 parts of bromoisobutyrylated cellulose acetate to obtain a mixture; A3. Place the mixture from step A2 into a reactor and carry out a polymerization reaction at a temperature of 140°C for 6 hours. After the reaction is complete, cellulose acetate grafted polylactic acid is obtained.

[0028] A method for preparing carbon nanotube-doped talc includes the following steps: B1. Add talc powder to a 1% sodium hydroxide solution, soak, filter, and calcine at a high temperature of 700℃ for 1 hour to obtain pretreated talc powder. B2. After removing the pretreated talc powder, quickly place it into a carbon nanotube dispersion with a mass concentration of 0.5% and N,N-dimethylformamide as the dispersing solvent for cooling. After filtration and drying, the carbon nanotube-doped talc powder is obtained.

[0029] Comparative Example 1 The only difference between this comparative example and Example 1 is that no pretreatment of the talc powder was performed in the preparation of the carbon nanotube-doped talc powder. Specifically, the talc powder was taken out and quickly placed into a carbon nanotube dispersion with a mass concentration of 0.3% and N,N-dimethylformamide as the dispersing solvent for cooling. After filtration and drying, the carbon nanotube-doped talc powder was obtained.

[0030] Comparative Example 2 The only difference between this comparative example and Example 1 is that polylactic acid is not grafted with cellulose acetate; that is, cellulose acetate grafted with polylactic acid is replaced with polylactic acid. The preparation method of polylactic acid includes the following steps: A1. Disperse 0.15 parts of zinc lactate catalyst in 10 parts of lactic acid monomer to obtain a dispersion; A2. Place the dispersion from step A2 into a reactor and carry out a polymerization reaction at a temperature of 130°C for 8 hours. After the reaction is complete, cellulose acetate-grafted polylactic acid is obtained.

[0031] Comparative Example 3 The only difference between this comparative example and Example 1 is that, in the preparation of carbon nanotube-doped talc, no pretreatment of talc was performed, and polylactic acid was not grafted with cellulose acetate.

[0032] Proof of effectiveness The biodegradable plastic masterbatches obtained in Examples 1-3 and Comparative Examples 1-3 were placed in an injection molding machine to prepare standard injection molding specimens. Test specimens were obtained, and tensile strength and tensile strength retention rate were tested. The specific test results are shown in Table 1. Tensile strength: The tensile strength I was measured according to the method specified in GB / T1040.2-2022 "Plastics - Determination of tensile properties - Part 2: Test conditions for molded and extruded plastics" at a tensile rate of 10 mm / min. Tensile strength retention rate: After placing the test specimen at a temperature of 60±2℃ and a humidity of 60±5% for 7×24h, the tensile strength is tested again according to the above method, and the tensile strength II is obtained; Tensile strength retention rate = (tensile strength II / tensile strength I)*100%.

[0033] Table 1 Tensile strength / MPa Tensile strength retention rate / % Example 1 48.4 72.2 Example 2 47.8 71.7 Example 3 48.1 71.9 Comparative Example 1 46.7 67.6 Comparative Example 2 47.2 66.3 Comparative Example 3 45.8 63.8 Results Analysis Analysis of Examples 1-3 and Comparative Examples 1-3, and in conjunction with Table 1, shows that the standard injection-molded specimens formed from the biodegradable plastic masterbatch (Examples 1-3) provided by the present invention are significantly better than those of the comparative examples in terms of tensile strength and tensile strength retention rate. This indicates that the biodegradable plastic masterbatch prepared by the present invention has high mechanical strength. After high-temperature treatment, it can still maintain high mechanical strength, indicating that the biodegradable plastic masterbatch has high heat resistance.

[0034] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0035] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A biodegradable plastic masterbatch, characterized in that, By weight, it includes the following components: 100 parts cellulose acetate-grafted polylactic acid, 15-25 parts polycaprolactone, 14-16 parts carbon nanotube-doped talc, 3-7 parts plasticizer, 1-5 parts compatibilizer, and 0.5-2 parts lubricant.

2. The biodegradable plastic masterbatch according to claim 1, characterized in that, The method for preparing cellulose acetate grafted with polylactic acid includes the following steps: A1. Dissolve cellulose acetate in a solvent, add bromoisobutyryl bromide and react to obtain bromoisobutyrylated cellulose acetate; A2. The catalyst is dispersed in lactic acid monomer to obtain a dispersion, and the dispersion is mixed with bromoisobutyrylated cellulose acetate to obtain a mixture; A3. The mixture from step A2 is subjected to a polymerization reaction. After the reaction is complete, cellulose acetate grafted polylactic acid is obtained.

3. The biodegradable plastic masterbatch according to claim 2, characterized in that, In step A2, the mass ratio of lactic acid monomer to bromoisobutyrylated cellulose acetate is 10:1.1-1.

3.

4. The biodegradable plastic masterbatch according to claim 1, characterized in that, A method for preparing carbon nanotube-doped talc includes the following steps: B1. Add talc powder to an alkaline solution, soak, filter, and calcine at high temperature to obtain pretreated talc powder; B2. The pretreated talc powder is placed in a carbon nanotube dispersion and rapidly cooled, then filtered and dried to obtain the carbon nanotube-doped talc powder.

5. The biodegradable plastic masterbatch according to claim 1, characterized in that, The plasticizer is one or a mixture of two or more of glycerol, polyglycerol, and ethylene glycol.

6. The biodegradable plastic masterbatch according to claim 1, characterized in that, The compatibilizer is one or a mixture of two or more of glycidyl methacrylate, L-lysine triisocyanate and maleic anhydride-grafted ethylene-octene copolymer.

7. The biodegradable plastic masterbatch according to claim 1, characterized in that, The lubricant is one or a mixture of calcium stearate and zinc stearate.

8. The biodegradable plastic masterbatch according to claim 4, characterized in that, The particle size of the talc powder satisfies: D95≤25μm.

9. A method for preparing biodegradable plastic masterbatch, used to prepare the biodegradable plastic masterbatch according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Grafting cellulose acetate onto polylactic acid, polycaprolactone, and carbon nanotubes doped with talc powder, and then melt-blending them in a twin-screw extruder, yields modified polylactic acid; S2. Modified polylactic acid is mixed evenly with the remaining raw materials, added to a twin-screw extruder for melt blending, and then extruded and granulated to obtain biodegradable plastic masterbatch.

10. The preparation method according to claim 9, characterized in that, The temperatures of each section of the extruder are as follows: Temperature control zone 1 180±2℃, temperature control zone 2 185±2℃, temperature control zone 3 190±2℃, and die head temperature 185±2℃.