Biodegradable reinforced plastic and preparation method thereof

Abstract

The invention discloses biodegradable reinforced plastic and a preparation method thereof, and relates to the technical field of degradable plastic. According to the invention, firstly, terephthalic acid and tartaric acid are esterified to introduce more hydroxyl groups and carboxyl groups into terephthalic acid, so that plastic skeletons with more hydroxyl and carboxyl functional groups are prepared in the further dehydration polymerization process, and cross-linking between the skeletons is further initiated to finally form a firm three-dimensional space network; the sodium hydroxide is used for pretreating the hollow glass beads, the cotton fiber nanocrystallines and the active hollow glass beads are further compounded to form a plastic reinforcing filler, and the plastic reinforcing filler is added into the plastic to enhance the mechanical property of the plastic. According to the biodegradable reinforced plastic prepared by the invention, on the basis of realizing biodegradability, the water resistance, plasticity and pressure resistance of the plastic are further enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of biodegradable plastics, in particular to a biodegradable reinforced plastic and a preparation method thereof. Background Art

[0002] Since its invention in the early 20th century, plastic has become one of the indispensable materials in modern society. Its wide application covers packaging, construction, transportation, electronic appliances, medical and other fields. However, with the surge in the use of plastics, the environmental pollution caused by waste plastics has become increasingly serious. According to statistics, more than 300 million tons of plastic waste are generated worldwide each year, of which less than 10% are effectively recycled, and most of the rest are either landfilled or directly enter the natural environment, causing serious pollution to ecosystems such as soil, rivers, and oceans. Traditional petroleum-based plastics have become long-term pollutants in the environment due to their difficult-to-degrade properties. For example, common polymer materials such as polyethylene (PE) and polypropylene (PP) take hundreds of years to be completely decomposed under natural conditions, during which time they will continue to release harmful substances, posing a threat to the ecological environment. In addition, plastics will gradually break into microplastics during the decomposition process. These microplastics can enter the bodies of animals and plants through the food chain, and ultimately cause potential harm to human health. In the face of the increasingly serious problem of plastic pollution, the development and application of biodegradable plastics is particularly important. Biodegradable materials refer to materials that can be degraded by biological erosion or metabolism under certain conditions, and the mechanism is biophysical reaction and biochemical reaction. According to their degradation characteristics, biodegradable materials include completely biodegradable materials and biodestructive materials. According to their sources, they can be divided into microbial synthetic materials, natural polymer materials, chemical synthetic materials, blended materials, etc. At present, there are many biodegradable plastic bags on the market, but most of them have technical problems of poor mechanical properties and cannot fully meet the needs of the market. Therefore, it is urgent to develop more biodegradable plastics with strong mechanical properties to meet the needs of the market. Summary of the invention

[0003] The object of the present invention is to provide a biodegradable reinforced plastic and a preparation method thereof, so as to solve the problems existing in the prior art.

[0004] In order to solve the above technical problems, the present invention provides the following technical solution: a biodegradable reinforced plastic, wherein the biodegradable reinforced plastic comprises polyester, reinforcing filler, plasticizer and compatibilizer.

[0005] Furthermore, the polyester is prepared by polymerizing terephthalic acid and tartaric acid.

[0006] Furthermore, the reinforcing filler is obtained by pretreating hollow glass beads with sodium hydroxide and then compounding with cotton fiber nanocrystals.

[0007] Furthermore, the plasticizer is one or both of dipropylene glycol dibenzoate and pentaerythritol.

[0008] Furthermore, the compatibilizer is any one or more of maleic anhydride, dioctyl maleate, diisocyanate and silane coupling agent.

[0009] Furthermore, a method for preparing a biodegradable reinforced plastic is characterized by comprising the following preparation steps:

[0010] (1) terephthalic acid, tartaric acid and tetrabutyl titanate are uniformly mixed and added into a polymerization reactor, and a pressure esterification reaction is carried out at 230-250° C. and 0.2-0.4 MPa. After the esterification water reaches 95% of the theoretical water output, a pre-condensation reaction is carried out at 250-270° C. and 500-700 Pa for 40-60 min, and the temperature is further raised to 270-290° C. and 70-100 Pa to complete the final condensation reaction. When the motor torque value of the reactor reaches 8 N·m, the material is discharged and pelletized to obtain polyester;

[0011] (2) taking 10 to 20 parts of dried hollow glass beads and placing them in 300 to 500 parts of a sodium hydroxide solution with a concentration of 0.2 to 0.6 mol / L, stirring at 65 to 85° C. and 300 to 400 r / min for 1 to 2 hours, cooling to room temperature, washing with deionized water until the pH is 6.8 to 7.2, filtering and drying at 90 to 120° C. for 1 to 4 hours to obtain pretreated hollow glass beads;

[0012] (3) mixing the pretreated hollow glass beads, anhydrous ethanol, and cotton fiber nanocrystals, stirring at 70-90° C. and 300-500 r / min for 3-5 h, cooling to room temperature, washing the product 3-6 times with 95% by volume ethanol, and filtering under reduced pressure, and drying at 80-120° C. for 4-6 h to obtain a reinforcing filler;

[0013] (4) The polyester, reinforcing filler, plasticizer and bulking agent are mixed, stirred and mixed at 60-90° C. and 500-800 r / m for 50-60 min. After mixing, the mixture is put into a twin-screw extruder for extrusion granulation.

[0014] Furthermore, in step (1), by weight, terephthalic acid is 30 to 50 parts, tartaric acid is 25 to 45 parts, and tetrabutyl titanate is 4 to 8 parts.

[0015] Furthermore, in step (3), the pretreated hollow glass beads are 20 to 40 parts, anhydrous ethanol is 50 to 60 parts, and cotton fiber nanocrystals are 35 to 55 parts by weight.

[0016] Furthermore, in step (4), by weight, 40 to 50 parts of tartaric acid terephthalate, 20 to 30 parts of composite plastic reinforcing filler, 10 to 20 parts of plasticizer, and 5 to 10 parts of compatibilizer are used.

[0017] Furthermore, the aspect ratio of the twin-screw extruder in step (5) is 50:1, and the extrusion temperature is 170-180°C.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0019] The biodegradable reinforced plastic prepared by the invention not only realizes biodegradability, but also effectively enhances the water resistance and compression resistance of the plastic.

[0020] Firstly, terephthalic acid is esterified with tartaric acid to introduce more hydroxyl and carboxyl groups into terephthalic acid, so that a plastic skeleton with more hydroxyl and carboxyl functional groups can be prepared in the process of further dehydration polymerization. This skeleton has high biodegradability. The hydroxyl and carboxyl functional groups on the side branches of the skeleton provide reactive active sites for the cross-linking between the plastic backbone chains in the later stage and the further modification and strengthening of the plastic, finally forming a strong three-dimensional spatial network. The modified and strengthened plastic shows higher hydrophobicity due to the consumption of hydroxyl and carboxyl groups, thereby enhancing the water resistance of the plastic.

[0021] Secondly, the hollow glass beads are pretreated with sodium hydroxide to obtain a large number of active hydroxyl sites on the surface of the hollow glass beads for grafting modification. Cotton fiber nanocrystals are further used to compound the active hollow glass beads to form plastic reinforcing fillers. When added to plastics, the hydroxyl groups in the cotton fiber nanocrystals can be dehydrated with the hydroxyl and carboxyl sites in the three-dimensional plastic skeleton to form ether bonds or ester bonds to combine together, thereby lowering the glass transition temperature of the plastic and improving the plasticity of the plastic. The hollow glass beads are naturally filled in the three-dimensional network. When the plastic is under pressure, the three-dimensional network is supported, thereby enhancing the compressive resistance of the plastic and improving the mechanical properties of the plastic. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the test methods of various indicators of the biodegradable reinforced plastics prepared in the following examples.

[0024] Preparation of injection molding standard specimens: The samples prepared in Examples 1-3 and Comparative Examples 1-4 were dried in a vacuum oven for 8 h, and then injection molded standard specimens according to GB / T17037.1-2019, with the barrel temperature set at 240°C;

[0025] Biodegradability: The biodegradability of the biodegradable reinforced plastics prepared in Examples 1-3 and Comparative Examples 1-4 was tested in accordance with GB / T20197-2006;

[0026] Water vapor permeability: The water vapor permeability test of the biodegradable reinforced plastics prepared in Examples 1-3 and Comparative Examples 1-4 was performed in accordance with GB / T1037-88;

[0027] Tensile properties: The biodegradable reinforced plastics prepared in Examples 1-3 and Comparative Examples 1-4 were tested for tensile properties in accordance with GB / T1040.2-2022;

[0028] Impact resistance: The impact resistance of the biodegradable reinforced plastics prepared in Examples 1-3 and Comparative Examples 1-4 was tested in accordance with GB / T1843-2008.

[0029] Example 1

[0030] (1) 30 parts of terephthalic acid, 25 parts of tartaric acid and 4 parts of tetrabutyl titanate are mixed uniformly and added into a polymerization reactor, and a pressure esterification reaction is carried out at 240° C. and 0.2 MPa. After the esterification water reaches 95% of the theoretical water output, a pre-polycondensation is carried out at 260° C. and 600 Pa for 50 minutes, and the temperature is further raised to 280° C. and 80 Pa to complete the final polycondensation. When the motor torque value of the reactor reaches 8 N·m, the material is discharged and pelletized to obtain polyester;

[0031] (2) taking 10 parts of dried hollow glass beads and placing them in 300 parts of a sodium hydroxide solution with a concentration of 0.4 mol / L, stirring at 75° C. and 350 r / min for 2 h, cooling to room temperature, washing with deionized water until the pH is 7.0, filtering and drying at 100° C. for 2 h to obtain pretreated hollow glass beads;

[0032] 30 parts of washed cotton fibers were dried in an oven at 70°C for 2 hours, immersed in 50 parts of isopropanol solution for 50 minutes, taken out and dried at 80°C for 3 hours, passed through an 80-mesh sieve to obtain cotton fiber powder, and then treated with 60 parts of 8% hydrogen peroxide at 70°C for 2 hours, washed, dried at 80°C for 2 hours, mixed with 60 parts of 60% sulfuric acid, stirred at 400r / min in a 60°C oil bath for 50 minutes, added with 600 parts of 8°C cold water, stopped the reaction, centrifuged at 5000r / m for 30 minutes, repeated centrifugation 6 times, dialyzed in deionized water for 5 days, and the water was changed every 12 hours until the suspension was neutral, to obtain cotton cellulose nanocrystals;

[0033] (3) 20 parts of pretreated hollow glass beads, 50 parts of anhydrous ethanol, and 35 parts of cotton fiber nanocrystals were mixed, stirred at 80° C. and 400 r / min for 4 h, cooled to room temperature, washed the product with 95% by volume ethanol for 5 times, and filtered under reduced pressure. After filtering, the product was dried at 90° C. for 5 h to obtain a reinforced filler;

[0034] (4) 40 parts of polyester, 20 parts of reinforcing filler, 10 parts of plasticizer and 5 parts of compatibilizer were mixed, stirred and mixed at 90°C and 800 r / m for 60 min, and after mixing, put into a twin-screw extruder with an aspect ratio of 50:1 and 180°C for extrusion granulation.

[0035] Example 2

[0036] (1) 40 parts of terephthalic acid, 35 parts of tartaric acid and 6 parts of tetrabutyl titanate are mixed uniformly and added into a polymerization reactor, and a pressure esterification reaction is carried out at 240° C. and 0.2 MPa. After the esterification water reaches 95% of the theoretical water output, a pre-polycondensation is carried out at 260° C. and 600 Pa for 50 minutes, and the temperature is further raised to 280° C. and 80 Pa to complete the final polycondensation. When the motor torque value of the reactor reaches 8 N·m, the material is discharged and pelletized to obtain polyester;

[0037] (2) taking 15 parts of dried hollow glass beads and placing them in 400 parts of a sodium hydroxide solution with a concentration of 0.4 mol / L, stirring at 75° C. and 350 r / min for 2 h, cooling to room temperature, washing with deionized water until the pH is 7.0, filtering and drying at 100° C. for 2 h to obtain pretreated hollow glass beads;

[0038] 30 parts of washed cotton fibers were dried in an oven at 70°C for 2 hours, immersed in 50 parts of isopropanol solution for 50 minutes, taken out and dried at 80°C for 3 hours, passed through an 80-mesh sieve to obtain cotton fiber powder, and then treated with 60 parts of 8% hydrogen peroxide at 70°C for 2 hours, washed, dried at 80°C for 2 hours, mixed with 60 parts of 60% sulfuric acid, stirred at 400r / min in a 60°C oil bath for 50 minutes, added with 600 parts of 8°C cold water, stopped the reaction, centrifuged at 5000r / m for 30 minutes, repeated centrifugation 6 times, dialyzed in deionized water for 5 days, and the water was changed every 12 hours until the suspension was neutral, to obtain cotton cellulose nanocrystals;

[0039] (3) 30 parts of pretreated hollow glass beads, 55 parts of anhydrous ethanol, and 45 parts of cotton fiber nanocrystals were mixed, stirred at 80° C. and 400 r / min for 4 h, cooled to room temperature, washed the product with 95% by volume ethanol for 5 times, and filtered under reduced pressure. After filtering, the product was dried at 90° C. for 5 h to obtain a reinforced filler;

[0040] (4) 45 parts of polyester, 25 parts of reinforcing filler, 15 parts of plasticizer and 8 parts of compatibilizer were mixed, stirred and mixed at 90°C and 800 r / m for 60 min, and after mixing, put into a twin-screw extruder with an aspect ratio of 50:1 and 180°C for extrusion granulation.

[0041] Example 3

[0042] (1) 50 parts of terephthalic acid, 45 parts of tartaric acid and 8 parts of tetrabutyl titanate are mixed uniformly and added into a polymerization reactor, and a pressure esterification reaction is carried out at 240° C. and 0.2 MPa. After the esterification water reaches 95% of the theoretical water output, a pre-polycondensation is carried out at 260° C. and 600 Pa for 50 minutes, and the temperature is further raised to 280° C. and 80 Pa to complete the final polycondensation. When the motor torque value of the reactor reaches 8 N·m, the material is discharged and pelletized to obtain polyester;

[0043] (2) taking 20 parts of dried hollow glass beads and placing them in 500 parts of a sodium hydroxide solution with a concentration of 0.4 mol / L, stirring at 75° C. and 350 r / min for 2 h, cooling to room temperature, washing with deionized water until the pH is 7.0, filtering and drying at 100° C. for 2 h to obtain pretreated hollow glass beads;

[0044] 30 parts of washed cotton fibers were dried in an oven at 70°C for 2 hours, immersed in 50 parts of isopropanol solution for 50 minutes, taken out and dried at 80°C for 3 hours, passed through an 80-mesh sieve to obtain cotton fiber powder, and then treated with 60 parts of 8% hydrogen peroxide at 70°C for 2 hours, washed, dried at 80°C for 2 hours, mixed with 60 parts of 60% sulfuric acid, stirred at 400r / min in a 60°C oil bath for 50 minutes, added with 600 parts of 8°C cold water, stopped the reaction, centrifuged at 5000r / m for 30 minutes, repeated centrifugation 6 times, dialyzed in deionized water for 5 days, and the water was changed every 12 hours until the suspension was neutral, to obtain cotton cellulose nanocrystals;

[0045] (3) 40 parts of pretreated hollow glass beads, 60 parts of anhydrous ethanol, and 55 parts of cotton fiber nanocrystals were mixed, stirred at 80° C. and 400 r / min for 4 h, cooled to room temperature, washed the product with 95% by volume ethanol for 5 times, and filtered under reduced pressure. After filtering, the product was dried at 90° C. for 5 h to obtain a reinforced filler;

[0046] (4) 50 parts of polyester, 30 parts of reinforcing filler, 20 parts of plasticizer and 10 parts of compatibilizer were mixed, stirred and mixed at 90°C and 800 r / m for 60 min, and after mixing, put into a twin-screw extruder with an aspect ratio of 50:1 and 180°C for extrusion granulation.

[0047] Comparative Example 1

[0048] The difference between Comparative Example 1 and Example 2 is that the tartaric acid in step (1) is replaced by lactic acid, and the remaining steps are the same as Example 2.

[0049] Comparative Example 2

[0050] The difference between Comparative Example 2 and Example 2 is that in step (2), only the hollow glass beads are pretreated, and the preparation of cotton fiber nanocrystals is omitted, step (3) is removed, and the reinforcing filler in step (4) is replaced by pretreated hollow glass beads, and the remaining steps are the same as in Example 2.

[0051] Comparative Example 3

[0052] The difference between Comparative Example 3 and Example 2 is that in step (2), the pretreatment of hollow glass beads is omitted, and only cotton fiber nanocrystals are prepared, step (3) is removed, and the reinforcing filler in step (4) is replaced by cotton fiber nanocrystals, and the remaining steps are the same as in Example 2.

[0053] Comparative Example 4

[0054] The difference between Comparative Example 4 and Example 2 is that step (2) and step (3) are removed, and no reinforcing filler is used in step (4). The remaining steps are the same as those in Example 2.

[0055] Effect example

[0056] Table 1 below shows the performance analysis results of the biodegradable reinforced plastics of Examples 1 to 3 of the present invention and Comparative Examples 1 to 4.

[0057] Table 1 Performance results of biodegradable reinforced plastics prepared in Examples 1-3 and Comparative Examples 1-4

[0058]

[0059]

[0060] From the test results in Table 1, we find that the biodegradable reinforced plastic prepared by the present invention has high biodegradability. The consumption of hydroxyl and carboxyl groups in the main skeleton makes it show a certain hydrophobicity to water, and the amount of water vapor permeation allowed is relatively small. The reinforcing filler used can effectively improve the mechanical properties of the plastic, showing good tensile strength and elongation at break, and the impact strength is also effectively improved.

[0061] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A biodegradable reinforced plastic, characterized in that: The biodegradable reinforced plastic comprises polyester, reinforcing filler, plasticizer and compatibilizer.

2. The biodegradable reinforced plastic according to claim 1, characterized in that: The polyester is prepared by polymerizing terephthalic acid and tartaric acid.

3. The biodegradable reinforced plastic according to claim 2, characterized in that: The reinforcing filler is obtained by pretreating hollow glass beads with sodium hydroxide and then compounding with cotton fiber nano-crystals.

4. The biodegradable reinforced plastic according to claim 3, characterized in that: The plasticizer is one or both of dipropylene glycol dibenzoate and pentaerythritol.

5. The biodegradable reinforced plastic according to claim 4, characterized in that: The compatibilizer is any one or more of maleic anhydride, dioctyl maleate, diisocyanate and silane coupling agent.

6. A method for preparing a biodegradable reinforced plastic, characterized in that: The method comprises the following preparation steps: (1) terephthalic acid, tartaric acid and tetrabutyl titanate are uniformly mixed and added into a polymerization reactor, and a pressure esterification reaction is carried out at 230-250° C. and 0.2-0.4 MPa. After the esterification water reaches 95% of the theoretical water output, a pre-condensation reaction is carried out at 250-270° C. and 500-700 Pa for 40-60 min, and the temperature is further raised to 270-290° C. and 70-100 Pa to complete the final condensation reaction. When the motor torque value of the reactor reaches 8 N·m, the material is discharged and pelletized to obtain polyester; (2) taking 10 to 20 parts of dried hollow glass beads and placing them in 300 to 500 parts of a sodium hydroxide solution with a concentration of 0.2 to 0.6 mol / L, stirring at 65 to 85° C. and 300 to 400 r / min for 1 to 2 hours, cooling to room temperature, washing with deionized water until the pH is 6.8 to 7.2, filtering and drying at 90 to 120° C. for 1 to 4 hours to obtain pretreated hollow glass beads; (3) mixing the pretreated hollow glass beads, anhydrous ethanol, and cotton fiber nanocrystals, stirring at 70-90° C. and 300-500 r / min for 3-5 h, cooling to room temperature, washing the product 3-6 times with 95% by volume ethanol, and filtering under reduced pressure, and drying at 80-120° C. for 4-6 h to obtain a reinforcing filler; (4) The polyester, reinforcing filler, plasticizer and bulking agent are mixed, stirred and mixed at 60-90° C. and 500-800 r / m for 50-60 min. After mixing, the mixture is put into a twin-screw extruder for extrusion granulation.

7. The method for preparing a biodegradable reinforced plastic according to claim 6, characterized in that: In step (1), by weight, 30 to 50 parts of terephthalic acid, 25 to 45 parts of tartaric acid, and 4 to 8 parts of tetrabutyl titanate are used.

8. The method for preparing a biodegradable reinforced plastic according to claim 6, characterized in that: In step (3), the pretreated hollow glass beads are 20 to 40 parts, anhydrous ethanol is 50 to 60 parts, and cotton fiber nanocrystals are 35 to 55 parts by weight.

9. The method for preparing a biodegradable reinforced plastic according to claim 6, characterized in that: In step (4), by weight, 40 to 50 parts of poly(tartrate terephthalate), 20 to 30 parts of composite plastic reinforcing filler, 10 to 20 parts of plasticizer, and 5 to 10 parts of compatibilizer are used.

10. The method for preparing a biodegradable reinforced plastic according to claim 6, characterized in that: The aspect ratio of the twin-screw extruder in step (5) is 50:1, and the extrusion temperature is 170-180°C.

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