PLA-PHA bamboo plastic composite material and preparation method thereof

Abstract

The application relates to the technical field of polylactic acid, and discloses a PLA-PHA bamboo plastic composite material and a preparation method thereof. Polylactic acid, polyhydroxyalkanoate, polyester-phosphate flame retardant, bamboo powder and an antibacterial agent are added into a mixer for mixing, then are melt-extruded through a double-screw extruder, granulated, and injection-molded through an injection molding machine to obtain the PLA-PHA bamboo plastic composite material. The polyester-phosphate flame retardant contains a large amount of ester groups, has good compatibility with the polylactic acid and the polyhydroxyalkanoate, is uniformly dispersed in the composite material, simultaneously contains a hyperbranched branched network molecular chain, forms a physical interpenetrating network with the polylactic acid and the polyhydroxyalkanoate, and has a good toughening effect; the composite material has good antibacterial property, toughness, limiting oxygen index and flame retardant performance. The composite material has good practical application in the fields of degradable packaging plastic bags, flame-retardant antibacterial environment-friendly building materials and the like.

Description

Technical Field

[0001] This invention relates to the field of polylactic acid technology, specifically to a PLA-PHA bamboo-plastic composite material and its preparation method. Background Technology

[0002] Aliphatic polyester materials, such as polylactic acid, polyhydroxyalkanoates, and polycaprolactone, have advantages such as good biocompatibility, biodegradability, and pre-processable properties. They can be made into films and sheets, and have wide applications in building materials, packaging, and medical supplies. Bamboo-plastic composite materials are mainly composed of bamboo powder and plastic, combining the advantages of wood and plastic. They are lower in cost, more environmentally friendly, and have excellent corrosion resistance and weather resistance, making them widely used.

[0003] Because polylactic acid (PLA) and polyhydroxyalkanoates (PHA) are flammable, the resulting plastics and bamboo-plastic composites have poor flame retardancy, making them unsuitable for applications requiring high fire safety. Typically, flame retardants are added, such as inorganic flame retardants like aluminum hydroxide, and organic flame retardants like bromine-based and phosphorus-based ones. Patent CN108774307B discloses a halogen-free flame-retardant PLA wood-plastic composite material and its preparation method. This involves reacting diphenylmethane diisocyanate with 9,10-dihydro-9-oxaphenanthroline-10-oxide to prepare a phosphorus-containing flame retardant that can improve the flame retardant properties of PLA wood-plastic composites. However, this patent does not improve the compatibility of the flame retardant with the wood-plastic composite material, which can affect the material's mechanical properties. Summary of the Invention

[0004] This invention solves the problem of poor mechanical strength and flame retardancy of PLA-PHA bamboo-plastic composite materials.

[0005] The technical solution of this invention: A method for preparing PLA-PHA bamboo-plastic composite material: (1) Hydroxyethyl acrylate and diethanolamine were added to ethanol in a ratio of (1-1.1) mol:1 mol. After the reaction, the low-boiling substances were removed by vacuum distillation, washed with diethyl ether, and dried to obtain 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester. The preparation reaction was as follows: .

[0006] (2) Add triethylamine and 2-hydroxyethyl 3-[bis(2-hydroxyethyl)amino]propionic acid to the reaction solvent, add phenyl dichlorophosphate dropwise, stir the reaction, filter, distill the filtrate under reduced pressure, wash with water and ethanol successively, and dry to obtain polyester-phosphate flame retardant. The preparation reaction formula is: .

[0007] (3) Polylactic acid, polyhydroxy fatty acid ester, polyester-phosphate flame retardant, bamboo, and antibacterial agent are added to a mixer and mixed. Then, the mixture is melt-extruded through a twin-screw extruder, granulated, and injection molded to obtain PLA-PHA bamboo-plastic composite material.

[0008] Furthermore, in (1), the ratio of hydroxyethyl acrylate to diethanolamine is (1-1.1) mol: 1 mol.

[0009] Furthermore, in (1), the reaction temperature is 45-50℃ and the reaction time is 1-1.5h.

[0010] Furthermore, in (2), the reaction solvent is tetrahydrofuran, 1,4-dioxane or N,N-dimethylformamide.

[0011] Furthermore, in (2), the reaction temperature is 20-60℃ and the reaction time is 15-18h.

[0012] Furthermore, in (2), the ratio of triethylamine, 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester, and dichlorophosphate phenyl ester is (3-3.3) mol: 1 mol: (1.41-1.47) mol.

[0013] Furthermore, in (3), the ratio of polylactic acid, polyhydroxy fatty acid ester, polyester-phosphate flame retardant, bamboo powder, and antibacterial agent is (65-85)g:(15-35)g:(3-8)g:(30-50)g:(0.2-0.5)g.

[0014] Furthermore, in (3), the temperature of sections 1-6 of the twin-screw extruder is 150-180℃, and the screw speed is 30-60r / min.

[0015] Furthermore, (3) the temperature of injection molding machine sections 1-3 is 170-180℃.

[0016] The beneficial technical effects of this invention are as follows: A polyester-phosphate flame retardant is obtained by polymerizing 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester and phenyl dichlorophosphate. This flame retardant is then melt-blended with polylactic acid, polyhydroxyalkanoates, bamboo powder, and a silver-loaded zirconium phosphate antibacterial agent, and molded to obtain a PLA-PHA bamboo-plastic composite material. The polyester-phosphate flame retardant contains a large number of ester groups, exhibiting good compatibility with PLA (polylactic acid) and PHA (polyhydroxyalkanoates), and is uniformly dispersed in the composite material. Simultaneously, it contains hyperbranched branched network molecular chains, forming a physical interpenetrating network with polylactic acid and polyhydroxyalkanoates, thus providing excellent toughening and improving the toughness, impact strength, and flexural strength of the composite material.

[0017] The polyester-phosphate flame retardant of the present invention contains phosphate flame retardant groups, which can improve the char formation of the material during combustion, increase the limiting oxygen index, and improve the flame retardant performance. When combined with a highly efficient and safe silver-loaded zirconium phosphate antibacterial agent, it is beneficial to improve the antibacterial performance of the material. It has good practical applications in flame-retardant, antibacterial, and environmentally friendly building materials, biodegradable packaging plastic bags, etc. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] Example 1: (1) Add 2.2 mol of hydroxyethyl acrylate and 2 mol of diethanolamine to 2.5 L of ethanol, heat to 50 °C, react for 1 h, remove low-boiling substances by vacuum distillation, wash with ether, and dry to obtain 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester.

[0020] (2) Add 3 mol of triethylamine and 1 mol of 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester to 4 L of tetrahydrofuran, add 1.47 mol of dichlorophosphate dropwise, stir and react at 20 °C for 2 h, then heat to 60 °C and stir and react for 15 h, filter, distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain polyester-phosphate flame retardant.

[0021] (3) 7.5 kg of polylactic acid (model NatureWorks 2100-2P, the same below), 2.5 kg of polyhydroxy fatty acid ester (model Yikeman EM10080, the same below), 300 g of polyester-phosphate flame retardant, 3 kg of bamboo powder (average particle size about 150 mesh, the same below), and 30 g of antibacterial agent (model Fujian Ruisen New Materials RS-KJ04, the main component is silver-loaded zirconium phosphate, the same below) were added to a mixer and mixed. Then, the mixture was melt-extruded through a twin-screw extruder. The temperatures of sections 1-6 were 150℃, 170℃, 180℃, 180℃, 185℃, and 175℃, and the screw speed was 30 r / min. The mixture was then granulated and injection molded. The temperatures of sections 1-3 were 170℃, 180℃, and 175℃, respectively, to obtain PLA-PHA bamboo-plastic composite material.

[0022] Example 2: (1) Add 2 mol of hydroxyethyl acrylate and 2 mol of diethanolamine to 2.5 L of ethanol, heat to 45 °C, react for 1.5 h, remove low-boiling substances by vacuum distillation, wash with ether, and dry to obtain 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester.

[0023] (2) Add 3 mol of triethylamine and 1 mol of 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester to 5 L of N,N-dimethylformamide, add 1.41 mol of phenyl dichlorophosphate dropwise, stir and react at 25 °C for 2 h, then heat to 50 °C and stir and react for 16 h, filter, distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain polyester-phosphate flame retardant.

[0024] (3) Add 6.5 kg of polylactic acid, 3.5 kg of polyhydroxy fatty acid ester, 450 g of polyester-phosphate flame retardant, 3.5 kg of bamboo powder and 50 g of antibacterial agent to a mixer and mix them. Then melt extrusion is performed through a twin-screw extruder. The temperatures of sections 1-6 are 150℃, 170℃, 180℃, 180℃, 185℃ and 175℃, and the screw speed is 30 r / min. Granulation is performed and injection molding is performed. The temperatures of sections 1-3 are 170℃, 180℃ and 175℃ to obtain PLA-PHA bamboo-plastic composite material.

[0025] Example 3: (1) Prepare 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester according to the method of Example 1.

[0026] (2) Add 3.3 mol of triethylamine and 1 mol of 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester to 5 L of tetrahydrofuran, add 1.47 mol of dichlorophosphate dropwise, stir and react at 20 °C for 3 h, then heat to 60 °C and stir and react for 12 h, filter, distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain polyester-phosphate flame retardant.

[0027] (3) Add 8.5 kg of polylactic acid, 1.5 kg of polyhydroxy fatty acid ester, 600 g of polyester-phosphate flame retardant, 4 kg of bamboo powder and 20 g of antibacterial agent to a mixer and mix. Then melt extrude through a twin-screw extruder. The temperatures of sections 1-6 are 150℃, 170℃, 180℃, 180℃, 185℃ and 175℃, and the screw speed is 60 r / min. Granulate and injection mold. The temperatures of sections 1-3 are 170℃, 180℃ and 175℃ to obtain PLA-PHA bamboo-plastic composite material.

[0028] Example 4: (1) Prepare 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester according to the method of Example 1.

[0029] (2) Add 4.3 mol of triethylamine and 1 mol of 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester to 5 L of 1,4-dioxane, add 1.9 mol of phenyl dichlorophosphate dropwise, stir and react at 20 °C for 3 h, then heat to 60 °C and stir and react for 14 h, filter, distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain polyester-phosphate flame retardant.

[0030] (3) Add 7kg polylactic acid, 3kg polyhydroxy fatty acid ester, 800g polyester-phosphate flame retardant, 5kg bamboo powder and 30g antibacterial agent to a mixer and mix. Then melt extrude through a twin-screw extruder. The temperatures of sections 1-6 are 150℃, 170℃, 180℃, 180℃, 185℃ and 175℃, and the screw speed is 60r / min. Granulate and injection mold. The temperatures of sections 1-3 are 170℃, 180℃ and 175℃ to obtain PLA-PHA bamboo-plastic composite material.

[0031] Comparative Example 1: (1) 7.5 kg of polylactic acid, 2.5 kg of polyhydroxy fatty acid ester, 3 kg of bamboo powder and 30 g of antibacterial agent were added to a mixer and mixed. Then, the mixture was melt-extruded through a twin-screw extruder. The temperatures of sections 1-6 were 150℃, 170℃, 180℃, 180℃, 185℃ and 175℃, and the screw speed was 30 r / min. The mixture was then granulated and injection molded. The temperatures of sections 1-3 were 170℃, 180℃ and 175℃, respectively, to obtain PLA-PHA bamboo-plastic composite material.

[0032] Comparative Example 2: (1) Add 3 mol of triethylamine and 1.5 mol of 1,4-butanediol to 4 L of tetrahydrofuran, add 1.47 mol of phenyl dichlorophosphate dropwise, stir and react at 20 °C for 2 h, then heat to 60 °C and stir and react for 15 h, filter and distill under reduced pressure, wash with water and ethanol in sequence, dry to obtain polyphosphate flame retardant.

[0033] (2) 7.5 kg of polylactic acid, 2.5 kg of polyhydroxy fatty acid ester, 300 g of polyphosphate flame retardant, 3 kg of bamboo powder and 30 g of antibacterial agent were added to a mixer and mixed. Then, the mixture was melt-extruded through a twin-screw extruder. The temperatures of sections 1-6 were 150℃, 170℃, 180℃, 180℃, 185℃ and 175℃, and the screw speed was 30 r / min. The mixture was then granulated and injection molded. The temperatures of sections 1-3 were 170℃, 180℃ and 175℃, respectively, to obtain PLA-PHA bamboo-plastic composite material.

[0034] Comparative Example 3: (1) Add 3 mol of triethylamine and 1 mol of trimethylolpropane to 4 L of tetrahydrofuran, add 1.47 mol of phenyl dichlorophosphate dropwise, stir and react at 20 °C for 2 h, then heat to 60 °C and stir and react for 15 h, filter and distill under reduced pressure, wash with water and ethanol in sequence, dry to obtain polyphosphate flame retardant.

[0035] (2) 7.5 kg of polylactic acid, 2.5 kg of polyhydroxy fatty acid ester, 300 g of polyphosphate flame retardant, 3 kg of bamboo powder and 30 g of antibacterial agent were added to a mixer and mixed. Then, the mixture was melt-extruded through a twin-screw extruder. The temperatures of sections 1-6 were 150℃, 170℃, 180℃, 180℃, 185℃ and 175℃, and the screw speed was 30 r / min. The mixture was then granulated and injection molded. The temperatures of sections 1-3 were 170℃, 180℃ and 175℃, respectively, to obtain PLA-PHA bamboo-plastic composite material.

[0036] The impact strength of the composite material was tested according to GB / T1043-2008 standard, and the flexural strength was tested according to GB / T 9341-2008 standard. The flame retardant properties were tested according to GB / T 2406.1-2008 standard.

[0037] Table 1 Properties of composite materials

[0038] Compared with Comparative Example 1, the PLA-PHA bamboo-plastic composite materials of Examples 1-4 contain a polyester-phosphate flame retardant, which contains a large number of ester groups and has good compatibility with PLA polylactic acid and PHA polyhydroxy fatty acid ester. It is uniformly dispersed in the composite material and contains hyperbranched branched network molecular chains, which form a physical interpenetrating network with polylactic acid and polyhydroxy fatty acid ester, playing a good toughening role and improving the toughness, impact strength and flexural strength of the composite material. At the same time, it contains phosphate flame retardant groups, which can improve the char formation of the material during combustion, playing a good flame retardant role and increasing the limiting oxygen index.

[0039] In Comparative Example 2, the polyphosphate flame retardant obtained by polymerizing 1,4-butanediol and phenyl dichlorophosphate does not contain ester groups or have hyperbranched branched network molecular chains, and the composite material has low flexural strength and impact strength.

[0040] The polyphosphate flame retardant obtained by polymerizing trimethylolpropane and phenyl dichlorophosphate in Comparative Example 3 does not contain ester groups, has poor compatibility with polylactic acid and polyhydroxy fatty acid esters, and the composite material has low flexural strength and impact strength.

[0041] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific experimental groups described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing PLA-PHA bamboo-plastic composite material, characterized in that, The preparation method is as follows: (1) Add triethylamine and 2-hydroxyethyl 3-[bis(2-hydroxyethyl)amino]propionic acid to the reaction solvent, add phenyl dichlorophosphate dropwise, stir the reaction, filter, distill the filtrate under reduced pressure, wash and dry to obtain polyester-phosphate flame retardant; (2) Polylactic acid, polyhydroxy fatty acid ester, polyester-phosphate flame retardant, bamboo powder and antibacterial agent are added to a mixer and mixed. Then, the mixture is melt-extruded through a twin-screw extruder, granulated, and injection molded to obtain PLA-PHA bamboo-plastic composite material. The ratio of triethylamine, 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester, and phenyl dichlorophosphate in (1) is (3-3.3) mol: 1 mol: (1.41-1.47) mol.

2. The preparation method of PLA-PHA bamboo-plastic composite material according to claim 1, characterized in that, The reaction solvent in (1) is tetrahydrofuran, 1,4-dioxane or N,N-dimethylformamide.

3. The preparation method of PLA-PHA bamboo-plastic composite material according to claim 1, characterized in that, The reaction temperature in (1) is 20-60℃ and the reaction time is 15-18h.

4. The preparation method of PLA-PHA bamboo-plastic composite material according to claim 1, characterized in that, The preparation method of the 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester is as follows: hydroxyethyl acrylate and diethanolamine in a ratio of (1-1.1) mol:1 mol are added to ethanol, heated to 45-50℃, stirred for 1-1.5 h, distilled under reduced pressure, washed, and dried to obtain 3-[bis(2-hydroxyethyl)amino]propionic acid-2-hydroxyethyl ester.

5. The method for preparing PLA-PHA bamboo-plastic composite material according to claim 1, characterized in that, The ratio of polylactic acid, polyhydroxy fatty acid ester, polyester-phosphate flame retardant, bamboo powder, and antibacterial agent in (2) is (65-85)g:(15-35)g:(3-8)g:(30-50)g:(0.2-0.5)g.

6. The method for preparing PLA-PHA bamboo-plastic composite material according to claim 1, characterized in that, The temperature of sections 1-6 of the twin-screw extruder in (2) is 150-180℃, and the screw speed is 30-60r / min.

7. The method for preparing PLA-PHA bamboo-plastic composite material according to claim 1, characterized in that, The temperature of the injection molding machine in sections 1-3 in (2) is 170-180℃.

8. A PLA-PHA bamboo-plastic composite material obtained by the preparation method according to any one of claims 1-7.

Images