Modified superfine rice hull powder reinforced PBAT full-degradable agricultural mulching film material and preparation method thereof
Technical Field
The invention belongs to the field of materials, and particularly relates to a modified superfine rice hull powder reinforced PBAT full-degradable agricultural mulching film material and a preparation method thereof.
Background
The agricultural mulching film material applied in large scale in the market at present is mainly prepared from polyethylene and polypropylene materials, can not be degraded by microorganisms, has the problems of difficult and incomplete recovery, remains in soil, influences the physical and chemical properties of the soil, is harmful to soil and water, generally can cause 6 to 30 percent reduction of crop yield when the residual mulching film per mu of soil reaches more than 4 kilograms according to the research surface of agricultural environment and sustainable development research institute of Chinese academy of agricultural sciences, and the development of biodegradable materials is considered to be one of important methods for replacing the non-degradable polymer materials in order to solve the environmental problem.
Polybutylene adipate terephthalate (PBAT) is the most representative of biodegradable polyester materials, compared with common plastics, the PBAT biodegradable polyester material has higher production cost, lower thermophysical property and mechanical property, thereby hindering the development and application of the PBAT biodegradable polyester material, by adding low cost fillers (natural fibers and cellulose derivatives) as reinforcing agents, is an effective method, not only can maintain the biodegradability of a matrix, but also can reduce the cost and improve the performance, but also has the problems of filler dispersion, interaction between the filler and the matrix and the like, particularly in the field of films, the film products are generally formed by blowing after melting, the thickness of the film is within 0.1mm, the requirement on the film forming property and the compatibility of the material is extremely high, and the film can be blown to break and can not be formed when the system is not good in dispersion and compatibility and blow molding is carried out.
The rice hull powder is a natural plant fiber, the surface of the rice hull powder contains a large number of polar functional groups such as hydroxyl, phenolic hydroxyl and the like, the rice hull powder has strong hydrophilicity and chemical polarity, the PBAT surface has a polar chemical structure (hydrophobicity) and high viscosity, the compatibility with the rice hull powder is not good, the dispersion of a filler is greatly influenced, the inherent hydrophilicity of the rice hull powder is reduced by frequently modifying the surface of the rice hull powder, so that the interaction between the rice hull powder and the PBAT is increased, for example, the invention application patent with the patent number of CN110128800A discloses a rice hull powder/PBAT biological-based fully degradable material and a preparation method, the mesh number of the selected rice hull powder is 600-800 meshes, the content is 20-40 parts, the rice hull powder is subjected to alkaline hydrolysis, washing, drying, sulfuric acid swelling, suction filtration washing, ultrasonic wall breaking treatment steps to obtain pre-treated rice hull powder, and silane coupling agent KH560 is adopted for coupling treatment, then mixing with other raw materials at high speed, extruding and granulating by a double screw to obtain the degradable plastic with better comprehensive performance and low cost. The patent application publication No. CN 111073326A discloses a preparation method of a rice hull powder/PBAT composite material, wherein a coupling agent is synthesized by taking terephthalamide, polyethylene glycol and anhydrous potassium carbonate powder as raw materials, the rice hull powder is coated by the coupling agent, the mesh number of the rice hull powder is 600-800 meshes, and the mass ratio of the rice hull powder to the PBAT is 1: 1, adding other auxiliary agents, and refining to obtain a rice hull powder/PBAT composite material with better mechanical property, water absorption and thermal property than the composite material without the coupling agent. However, as shown in fig. 7, the mechanical properties are poor, the obtained film is easily blown to break and is difficult to continuously form, and the surface of the film is very rough.
The noun explains:
PBAT: thermoplastic biodegradable plastics.
BPO: benzoyl peroxide.
PLA: polylactic acid.
Disclosure of Invention
In order to solve the problems, the invention provides a modified superfine rice hull powder reinforced PBAT full-degradable agricultural mulching film material and a preparation method thereof. The superfine modified rice hull powder prepared by the method directly adopts the rice hull raw material and adopts a low-temperature crushing process, the manufacturing process is simple, no pollution is caused, the processing cost is low, the particle size is uniform, the specific surface area is large, the dispersibility is good, and the rice hull powder and a PBAT parent have better compatibility; the degradable mulching film material has good comprehensive properties such as appearance, film forming property and mechanical property, and the degradation period of the film material can be regulated and controlled within a certain range by adjusting the formula) so as to meet the requirements of different climatic conditions and different crop growth periods, and provide more choices for the application and development of the degradable mulching film material.
In order to achieve the technical effects, the technical scheme of the invention is as follows:
the modified superfine rice hull powder reinforced PBAT full-degradation agricultural mulching film material comprises main materials and auxiliary materials, and is characterized in that the main materials comprise 55-90% of PBAT, 5-20% of modified superfine rice hull powder, 0-15% of PLA and 1-10% of PBAT-g-MAH by weight; the auxiliary materials comprise 0.1-0.8% of nucleating agent, 0.1-0.5% of chain extender, 0-0.5% of anti-hydrolysis stabilizer, 0-2% of melt reinforcing agent, 0.2-2% of plasticizer, 0-0.5% of antioxidant, 0-0.5% of anti-ultraviolet agent, 0.2-0.8% of antibacterial agent and 0-0.5% of carbon black in weight of the main materials.
Further improvement, the preparation method of the modified superfine rice hull powder is as follows: crushing a rice hull raw material at a temperature of between 10 ℃ below zero and 5 ℃ below zero, screening to obtain powder with a mesh number of between 1250 and 5000 meshes, adding the powder into a high-speed stirrer, stirring for 2 to 5 minutes at a temperature of between 95 and 105 ℃, removing water to obtain dry powder, gradually adding a surface treatment agent into the high-speed stirrer, and stirring for 5 to 10 minutes to obtain a mixture; cooling the mixture to below 30 ℃, and then drying the mixture in an oven at 80 ℃ for 2 hours to obtain modified superfine rice hull powder; the addition amount of the surface treatment agent is 1-7% of the mass of the dry powder.
In a further improvement, the surface treating agent is one or any mixture of tung oil anhydride and octadecane.
In a further improvement, the manufacturing method of the PBAT-g-MAH comprises the following steps: adding 100 parts by weight of PBAT, 0.1-0.2 part by weight of BPO, 1-3 parts by weight of maleic anhydride and 0.1-0.3 part by weight of antioxidant into a high-speed stirrer, stirring for 3-5 min, adding into a screw granulator after stirring uniformly, extruding and granulating at 130-150 ℃, and drying to obtain PBAT-g-MAH.
In a further improvement, the nucleating agent is one or more of aryl hydrazide, trimesic acid amide, phenylphosphonate and dicarboxylic acid salicylic acid hydrazide; the hydrolysis-resistant stabilizer is one or more of carbodiimide and anhydride; the antioxidant is one or more of a phenol antioxidant, a phosphite antioxidant and a metal ion passivator; the plasticizer is one or more of polyester, phosphate ester, isosorbide diester, citric acid esters and castor oil derived ester.
In a further improvement, the melt reinforcing agent is an acrylate; the anti-ultraviolet agent is a UV absorbent; the antibacterial agent is an inorganic antibacterial agent which is one or more of dissolved glass particles containing antibacterial silver ions, nano silver ceramic powder composite antibacterial agent, zinc oxide, copper oxide, ammonium dihydrogen phosphate and lithium carbonate; the chain extender is one or more of epoxy functionalized chain extender, oxazoline chain extender, isocyanate chain extender and diphenylmethane diisocyanate.
A preparation method of a modified superfine rice hull powder reinforced PBAT full-degradable agricultural mulching material comprises the following steps:
preparing a main material according to 55-90% of PBAT, 5-20% of modified superfine rice hull powder, 0-15% of PLA and 1-10% of PBAT-g-MAH, then weighing 0.1-0.8% of nucleating agent, 0.1-0.5% of chain extender, 0-0.5% of hydrolysis resistant stabilizer, 0-2% of melt reinforcing agent, 0.2-2% of plasticizer, 0-0.5% of antioxidant, 0-0.5% of anti-ultraviolet agent, 0.2-0.8% of antibacterial agent and 0-0.5% of carbon black as auxiliary materials, and then putting the main material and the auxiliary materials into a low-speed stirring pot to stir for 2-5 minutes to obtain a uniform mixture;
step two, putting the uniform mixture into a double-screw extruder, extruding at the temperature of 130-150 ℃ and at the main machine rotating speed of 150-350 r/min, and heating, melting, mixing, bracing, cooling and granulating to obtain the superfine rice hull powder modified PBAT composite material;
step three, the preparation method of the mulching film comprises the following steps: and (3) passing the superfine rice hull powder modified PBAT composite material through a film blowing machine, and adjusting film blowing parameters to prepare the modified superfine rice hull powder reinforced PBAT full-degradable agricultural mulching film with different thicknesses.
The invention has the advantages that:
1. the superfine modified rice hull powder prepared by the invention directly adopts the rice hull raw material and adopts the low-temperature crushing process, the manufacturing process is simple, the pollution is avoided, the processing cost is low, the particle size is uniform, the specific surface area is large, the dispersibility is good, the rice hull powder and a PBAT parent have better compatibility,
2. the rice hull powder/PBAT full-degradable mulching film material prepared by the invention has good comprehensive properties such as appearance, film-forming property, mechanical property and the like, the degradation cycle of the film material can be regulated and controlled within a certain range by regulating and controlling the formula (by regulating and controlling the hydrolysis resistant agent, the antibacterial agent and the rice hull powder, wherein the hydrolysis resistant agent can react with terminal carboxyl, terminal amino and terminal hydroxyl generated in the hydrolysis of a polymer to produce a stable harmless product, the further degradation and chain scission are effectively prevented, the antibacterial agent can slowly release a small amount of silver ions in a humid environment, the silver ions can destroy the electrolyte balance of bacteria to cause the cell walls of the bacteria to be damaged and dead, the silver ions enter the bacteria to react and combine with the cellular enzymes of the bacteria to inhibit the activity of the cellular enzymes and the reproduction and regeneration of the bacteria, the effect of killing the bacteria is achieved, the degradation cycle is prolonged, the rice hull powder is a biological material, can provide attachment and nutrients for bacteria, increase the propagation of the bacteria and accelerate the biodegradation process. ) The material is made into a film by extrusion blow molding, and the prepared film can meet the national standard requirements of full-biodegradable agricultural ground covering films. The application of the rice hull powder/PBAT composite material in the field of film products is widened, and more choices are provided for the application and development of the degradable mulching film material.
Drawings
FIG. 1 is a process flow diagram of modified superfine rice hull powder.
FIG. 2 is a 1000-fold electron microscope image of modified superfine rice hull powder.
FIG. 3 is a 5000 times electron microscope image of modified superfine rice hull powder.
FIG. 4 is a perspective view of a modified superfine rice hull powder reinforced PBAT fully-degradable agricultural mulching film;
FIG. 5 is a top view of the modified superfine rice hull powder reinforced PBAT fully-degradable agricultural mulching film;
FIG. 6 is a schematic diagram of the mechanism of the present invention;
FIG. 7 is a PBAT/rice hull powder composite with poor film forming properties.
Detailed Description
The technical means of the present invention will be specifically described below by way of specific embodiments.
A preparation method of a modified superfine rice hull powder reinforced PBAT full-degradable agricultural mulching film material comprises the following steps:
1. preparation method of modified superfine rice hull powder (self-made)
Putting a rice hull raw material into a low-temperature knife disc type grinding machine, carrying out coarse crushing, controlling the temperature to be-10 to-5 ℃, and processing the rice hulls to 100 to 300 meshes to obtain rice hull powder A;
the method comprises the steps of putting rice hull powder A into an ultrafine powder grinding machine, wherein the rice hull powder A mainly comprises a low-temperature system, a grinding main machine, a control cabinet, a four-stage cyclone separator, a pulse dust removal box and the like, the temperature is controlled to be-10 ℃ to-5 ℃, grinding is carried out through a hammer blade rotating at high speed, the grinding fineness is controlled by adjusting the intermittence of a grading knife and a grading disc, the ground material enters the four-stage cyclone separator under the action of a centrifugal force and a draught fan, the rice hull powder is subjected to fineness grading, then the discharged material is collected through a cloth bag, the discharged material with unqualified particle size is continuously put into the ultrafine powder grinding machine, the discharged material with qualified particle size (the mesh size is 1250-5000 meshes) is obtained to obtain rice hull powder B, tail dust enters the pulse dust removal box, the rice hull powder is recycled after being filtered by a filter drum, no dust flies in the grinding process.
Adding the rice hull powder B into a high-speed stirrer, stirring for 2-5 minutes at 95-105 ℃, removing water, adding 1-7% of a surface treating agent according to the weight ratio of the rice hull powder, uniformly and slowly adding the rice hull powder into the high-speed stirrer, stirring for 5-10 minutes, then discharging the rice hull powder into a cooling stirring pot, reducing the temperature to below 30 ℃, drying the modified rice hull powder in an oven at 80 ℃ for 2 hours, and discharging the obtained modified superfine rice hull powder, wherein the particle size is uniform, the dispersibility is good, and the specific figure is shown in an electron microscope picture shown in figure 2 and figure 3.
A preparation method of PBAT-g-MAH comprises the following steps:
the raw materials comprise, by weight, 100 parts of PBAT, 0.1-0.2 part of BPO, 1-3% parts of maleic anhydride and 0.1-0.3 part of antioxidant, wherein the PBAT, the maleic anhydride, the BPO and the antioxidant are mixed in proportion and then stirred for 3-5 min by a high-speed stirrer to fully disperse the materials; and extruding, granulating and drying the mixed material at 130-150 ℃ to obtain PBAT-g-MAH.
3. Preparing a modified superfine rice hull powder reinforced PBAT full-degradable agricultural mulching film material:
weighing the raw materials and the auxiliary agents according to the formula, putting the raw materials and the auxiliary agents into a low-speed stirring pot, stirring for 2-5 minutes, discharging, putting the mixture into a double-screw extruder, extruding at the temperature of 130-150 ℃ and at the main engine rotating speed of 150-350 r/min, and heating, melting, mixing, drawing strips, cooling and granulating to obtain the superfine rice hull powder modified PBAT composite material.
The preparation method of the mulching film comprises the following steps: the rice hull powder modified PBAT composite material is processed by a film blowing machine to prepare agricultural mulching films with different thicknesses by adjusting film blowing parameters, and the agricultural mulching films are shown in figures 4 and 5.
The action mechanism is as follows: 1) the rice hull powder is rich in hydroxyl on the surface and can be subjected to esterification reaction with acid anhydride. The tung oil anhydride is used for carrying out esterification reaction with the surface hydroxyl of the rice hull powder, and the tung oil anhydride is introduced, so that the thermal stability of the rice hull powder is improved, and the internal toughness of the composite material is improved.
2) The preparation method comprises the steps of preparing maleic anhydride grafted PBAT (MAH-g-PBAT), introducing oxygen-containing functional groups on a PBAT molecular chain, improving the polarity of the composite material, improving the compatibility with tung oil anhydride modified rice hull powder, improving the interface compatibility of PBAT/modified rice hull powder by utilizing the Lorentz force of intermolecular polar groups, and improving the interface strength, so that the physical properties of the composite material are improved, and the method is specifically shown in figure 6.
Wherein the formula is respectively as follows:
the properties of the products prepared by the three formulas are as follows:
the above description is only one specific guiding embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modification of the present invention using this concept shall fall within the scope of the invention.