CN114196180B - Preparation method of coffee shell carbon/degradable plastic PHBV composite material - Google Patents

Abstract

The invention relates to a preparation method of a coffee shell carbon/degradable plastic PHBV composite material. The method comprises the following steps: the coffee shell carbon obtained by high-temperature carbonization after the coffee shell is crushed and PHBV are dried, and the mixture which is uniformly mixed and stirred is put into an extruder for mixing and granulating; and (5) placing the granulated material into an injection molding machine for injection molding to prepare the coffee shell carbon/PHBV composite material. The manufacturing process is simple; the prepared composite material has excellent thermal stability, high strength, degradability and environment friendliness. The carbon powder content in the composite material can reach 60%, so that the use amount of plastics is greatly reduced, and the cost is saved; can also fix carbon and play a role in carbon sealing.

Description

Preparation method of coffee shell carbon/degradable plastic PHBV composite material

technical field

The invention relates to a method for preparing a coffee shell charcoal/degradable plastic PHBV composite material, and belongs to the field of biomass composite materials.

technical background

Plastics are mostly developed from non-renewable petroleum and are non-degradable, which causes "white pollution". The quest to replace petroleum-based plastics with degradable and biorenewable materials is imperative today. Poly(β-hydroxybutyric acid and β-hydroxyvaleric acid) (PHBV) is a new type of polymer with good degradability, biocompatibility and excellent processability. It is used in the food packaging industry , cosmetics industry, agriculture and medical industry have a wide range of applications. However, PHBV, like other polymer materials, has a high viscosity that makes processing difficult, has strong hydrophobic properties, and has poor thermal stability, which further limits its performance and application in composite materials.

In order to improve some of the shortcomings of poly(β-hydroxybutyric acid and β-hydroxyvaleric acid) (PHBV), most of the current biomass micro-nano fibers are used to strengthen PHBV. Toughness and flame retardancy are significantly improved. However, the preparation of micro-nanofibers inevitably requires a large amount of chemical reagents and energy consumption. Secondly, biomass fibers have hydrophilic groups, while PHBV is a strongly hydrophobic material, which makes the interfacial compatibility of materials poor.

About 20% of the coffee bean shells will be produced during the shelling, polishing and grading process of coffee shelled beans. As a waste in the coffee production process, if the coffee bean shells are not treated scientifically and effectively, it will not only cause a huge waste of resources Waste, and bring serious pollution to the environment.

Contents of the invention

The object of the present invention is to provide a method for preparing coffee shell charcoal/degradable plastic PHBV composite material. The method has simple preparation process, easy processing and molding, and can overcome the problem of difficult processing and molding caused by the high viscosity of PHBV; the obtained composite material has excellent thermal stability, good mechanical strength, can reduce plastic and fix carbon, can be degraded by itself, and is environmentally friendly.

To achieve the above object, technical scheme of the present invention:

The preparation method of coffee shell charcoal/degradable plastic PHBV composite material comprises the steps:

(1) Pulverize the coffee shell and carry out high-temperature carbonization under an argon atmosphere;

(2) Sieve after pulverizing the coffee shell charcoal powder to obtain charcoal powder with different particle sizes;

(3) Dry the charcoal powder in a blast drying oven to an absolute dry state; place the PHBV in a blast drying oven and dry at 80°C for 24 hours;

(4) Stir the carbon powder and PHBV evenly in proportion to obtain a blended powder mixture; in the mixture, the carbon powder is 50wt% to 60wt%;

(5) The mixture is placed in a twin-screw extruder to melt, knead and granulate;

(6) Place the granulated material in an injection machine for injection molding.

The above-mentioned preparation method of coffee shell charcoal/degradable plastic PHBV composite material, the carbonization step in the step (1): heat the coffee shell from normal temperature to 400°C and then keep it warm; then continue to heat up to 800°C and keep it warm; then cool to room temperature ; The holding time is 2 hours.

In the preparation method of the above-mentioned coffee shell charcoal/degradable plastic PHBV composite material, the charcoal powder obtained by sieving in the step (2) has a mesh size of 80-1000 mesh.

In the above method for preparing the coffee shell charcoal/degradable plastic PHBV composite material, the internal temperature of the extruder in the step (5) is 165-180° C., and the screw speed is 10-50 rpm.

In the preparation method of the above coffee shell charcoal/degradable plastic PHBV composite material, in the step (4), the content of carbon powder in the mixture is 60wt%.

In the preparation method of the above-mentioned coffee shell charcoal/degradable plastic PHBV composite material, in the step (6), the injection temperature is 175°C to 180°C, the injection pressure is 10MPa, the movement speed of the injection head is 80mm/s, and the mold temperature is 70 ℃.

Beneficial effects of the present invention:

(1) The plastic used in the present invention is poly(β-hydroxybutyric acid and β-hydroxyvaleric acid) (PHBV), which is degradable and renewable. The invention uses discarded coffee bean shells as raw materials, and the coffee shell charcoal obtained after high-temperature carbonization has rich pore structure and high specific surface area, and is easy to compound with polymers. The carbon content of the prepared composite material is as high as 60%, which can effectively reduce the cost of the composite material, and can also fix carbon, play the role of carbon sequestration, and have great social benefits.

(2) It is easy to process and form carbon powder into PHBV, which can overcome the problem of difficulty in processing and forming due to the high viscosity of PHBV. The coffee shell contains oil, and the made coffee shell charcoal plays a certain lubricating role in the extrusion molding process of the composite material. The invention prepares the composite material with excellent performance without the need of auxiliary agents, has simple manufacturing process, and reduces the production cost of the enterprise.

(3) Compared with the problem of poor interfacial compatibility of biomass fiber/plastic composite materials, the hydrophilic groups on the surface of coffee shell carbon powder after high-temperature carbonization are greatly reduced, and have a three-dimensional perforated structure; the plastic is melted at high temperature and penetrates to the In these pores, a three-dimensional network structure is formed, and the two-phase interface has good bonding performance. The composite material has high mechanical strength and excellent thermal stability.

Description of drawings

Accompanying drawing 1 is the scanning electron microscope picture (magnification is 1000 times) of the sample tensile section of composite material obtained in Example 2.

Accompanying drawing 2 is the scanning electron microscope picture (magnification is 2000 times) of the sample stretching section of the composite material obtained in Example 2.

Accompanying drawing 3 is PHBV, the coefficient of thermal expansion figure of the composite material obtained in embodiment 1-2 in the temperature range of -30～60 ℃.

In Figure 3, "CSC:PHBV 6:4" and "CSC:PHBV 5:5" both refer to coffee shell charcoal/degradable plastic composite materials, and the contents of coffee shell charcoal powder and degradable plastic are 60% and 40% respectively , 50%, 50%. The ordinate in Fig. 3 is the coefficient of thermal expansion, the unit is 10 ^-6 /K.

Detailed ways

The preparation method of coffee shell charcoal/degradable plastic PHBV composite material, its steps:

(1) Pulverize the coffee shells, and pass in argon gas for high-temperature carbonization: the first stage is heated from normal temperature to 400°C and then kept warm; then the second stage is heated to 800°C to keep warm; cooled to room temperature; the heat preservation time is 2 hours.

(2) The coffee shell charcoal powder prepared in step (1), crush the charcoal powder with a pulverizer at 15000-25000rpm, and sieve the charcoal powder with a certain particle size with a standard sieve; place the charcoal powder at 105°C for blasting Dry in a drying oven for 48 hours, and dry to a dry state;

(3) Dry the poly(β-hydroxybutyric acid and β-hydroxyvaleric acid) (PHBV) powder in an air-blast drying oven at 80°C for 24 hours;

(4) take carbon powder and PHBV powder of different quality with electronic balance;

(5) Put the powder weighed in step (4) into a high-speed mixer according to the proportion and stir evenly to obtain a blended powder mixture. The stirring time is 5-8mins; see the examples for the dosage ratio of carbon powder and PHBV.

(6) Place the two material mixtures in step (5) in a twin-screw extruder for melt kneading and granulation. The internal temperature of the extruder is 165-180° C., and the screw speed is 25-45 rpm. For details, refer to the examples;

(7) Place the granulated material in an injection machine for injection molding. The injection temperature is 175°C, the injection pressure is 10MPa, the movement speed of the injection head is 80mm/s, and the mold temperature is 70°C.

Example 1

Use coffee shell charcoal as filler, choose coffee shell charcoal with a mesh number of 200, and the filling amount is 50wt%, and the addition amount of PHBV is 50wt%, put the two materials into a blender for blending, and put them into the extrusion after mixing evenly Mixing and granulation in the machine. The temperature inside the extruder was 175°C and the screw speed was 25 rpm. The granulated material is placed in an injection machine for injection molding. The tensile strength of the coffee shell charcoal/PHBV composite obtained by injection molding is 27.0MPa, and the tensile modulus is 2516.4MPa. The thermal expansion coefficient of the composite material obtained in Example 1 was tested, and the results are shown in Figure 3. The linear thermal expansion coefficient in the temperature range of -30 to 60°C was 46.2×10 ^-6 /K.

Example 2

Use coffee shell charcoal as a filler, select coffee shell charcoal with a mesh number of 200, and its filling amount is 60wt%, and the addition amount of PHBV is 40wt%, put the two materials into a blender for blending, and put them into the extrusion Mixing and granulation in the machine. The temperature inside the extruder was 175°C and the screw speed was 30 rpm. The granulated material is placed in an injection machine for injection molding. The tensile strength of the coffee shell charcoal/PHBV composite obtained by injection molding is 36.5MPa, and the tensile modulus is 2710MPa. The thermal expansion coefficient of the composite material obtained in Example 2 was tested, and the results are shown in Figure 3. The linear thermal expansion coefficient in the temperature range of -30 to 60°C was 41.5×10 ^-6 /K.

Example 3

Use coffee shell charcoal as a filler, select coffee shell charcoal with a mesh number of 300, and the filling amount is 50wt%, and the addition amount of PHBV is 50wt%, put the two materials into a blender for blending, and put them into the extrusion after mixing evenly Mixing and granulation in the machine. The temperature inside the extruder was 180° C., and the screw speed was 45 rpm. The granulated material is placed in an injection machine for injection molding.

Example 4

Use coffee shell charcoal as a filler, select coffee shell charcoal with a mesh number of 400, and the filling amount is 60wt%, and the addition amount of PHBV is 40wt%, put the two materials into a blender for blending, and put them into the extrusion Mixing and granulation in the machine. The temperature inside the extruder was 175°C and the screw speed was 25 rpm. The granulated material is placed in an injection machine for injection molding.

Example 5

Use coffee shell charcoal as a filler, select coffee shell charcoal with a mesh number of 500, and the filling amount is 60wt%, and the addition amount of PHBV is 40wt%, put the two materials into a blender for blending, and put them into the extrusion Mixing and granulation in the machine. The internal temperature of the extruder was 180° C., and the screw speed was 30 rpm. The granulated material is placed in an injection machine for injection molding.

Test method for thermal expansion coefficient of degradable plastics, coffee shell charcoal/degradable plastic composites: Take a sample with a length of 20mm, a width of 5mm, and a thickness of 1mm, and test it through a static mechanical thermal analyzer (TMA), tensile mode, nitrogen atmosphere, The heating rate was 5°C/min, the temperature range was -30°C to 60°C, the load was 0.03N, and each sample was tested five times. Calculate the thermal expansion coefficient in the temperature range of -30°C to 60°C, and take the average value.

The invention adds high-temperature carbonized carbon powder into the PHBV to improve its performance. Charcoal powder is derived from coffee bean husks and is a by-product of the industrial production of coffee beans. The invention uses discarded coffee bean shells as raw materials, and after high-temperature carbonization, the coffee shell charcoal has rich pore structure and high specific surface area, and is easy to compound with polymers. In the present invention, composite materials with excellent performance can be produced with or without additives, and the production process is simple, which reduces the production cost of enterprises.

Claims (5)

1. the preparation method of coffee shell charcoal/degradable plastic PHBV composite material is characterized in that comprising the steps: (1) Pulverize the coffee shell, and carry out high-temperature carbonization under an argon atmosphere; when carbonizing, the coffee shell is heated from normal temperature to 400°C and then kept warm; then continue to heat up to 800°C to keep warm; then cool to room temperature; the holding time is 2 hours; (2) Sieve after pulverizing the coffee shell charcoal powder to obtain charcoal powder with different particle sizes; (3) Dry the charcoal powder in a blast drying oven to an absolute dry state; place the PHBV in a blast drying oven and dry at 80°C for 24 hours; (4) Stir the carbon powder and PHBV evenly in proportion to obtain a blended powder mixture; in the mixture, the carbon powder is 50wt% to 60wt%; (5) The mixture is placed in a twin-screw extruder to melt, knead and granulate; (6) Place the granulated material in an injection machine for injection molding. 2. The preparation method of coffee shell charcoal/degradable plastic PHBV composite material according to claim 1, characterized in that: the charcoal powder obtained by sieving in the step (2) has a mesh size of 80-1000 mesh. 3. The preparation method of coffee shell charcoal/degradable plastic PHBV composite material according to claim 1, characterized in that: the internal temperature of the extruder in the step (5) is 165-180° C., and the screw speed is 10-100° C. 50 rpm. 4. The preparation method of coffee shell charcoal/degradable plastic PHBV composite material according to claim 1, characterized in that: in the step (4), the content of carbon powder in the mixture is 60wt%. 5. The preparation method of coffee shell charcoal/degradable plastic PHBV composite material according to claim 1, characterized in that: in the step (6), the injection temperature is 175°C-180°C, the injection pressure is 10MPa, and the injection The head movement speed is 80mm/s, and the mold temperature is 70°C.