1. The sheet-grade full-biodegradable polyester is characterized by comprising the following raw materials in parts by weight: 45% of corn starch, 20% of filler, 20% of polybutylene adipate-co-terephthalate PBAT 10%, 10% of polylactic acid PLA, 5% of plasticizer, 1% of compatilizer, 4% of stabilizer, 3% of dispersant, 0.02% of initiator and cross-linking agent, 1.97% of lubricant and 0.01% of chain extender; the filler adopts calcium carbonate, the plasticizer adopts glycerol, the compatilizer adopts maleic anhydride, the stabilizer adopts stearic acid, the dispersant adopts polyethylene wax, the initiator and the crosslinking agent adopt dicumyl peroxide (DCP), and the lubricant adopts white oil.

2. The sheet-grade fully biodegradable polyester according to claim 1, wherein the fineness of the calcium carbonate is more than 1500 meshes.

3. A preparation process of sheet-level full-biodegradable polyester is characterized by comprising the following preparation steps:

(1) uniformly mixing corn starch and stearic acid, and putting the mixture into a refiner for refining;

(2) placing the refined starch into a high-temperature mixer according to the formula proportion, stirring for 10-15min, controlling the temperature at 100 ℃ and 110 ℃, and volatilizing the moisture in the starch;

(3) adding glycerol, stirring for 5min, and controlling the temperature at 120-;

(4) adding calcium carbonate, stirring for 1min to uniformly mix the calcium carbonate and the starch;

(5) adding maleic anhydride and stirring for 3min, and controlling the temperature at 120-130 ℃;

(6) adding polyethylene wax and stirring for 2min, and controlling the temperature at 120-130 ℃;

(7) adding polybutylene adipate-butylene terephthalate copolymer PBAT, polylactic acid PLA and a chain extender, stirring for 4min, and controlling the temperature at 130-150 ℃;

(8) adding dicumyl peroxide (DCP) and white oil, stirring for 2min, and controlling the temperature at 130-150 ℃;

(9) gradually agglomerating the materials along with the rise of the temperature of the materials, opening volatilization holes to fully volatilize water, opening a discharge valve when the material agglomerates are gradually dispersed, starting a cold pot to stir, slowly feeding the materials into the cold pot, immediately putting the materials into a cooling stirrer after the materials are modified in a high-speed mixing modification machine, stirring for 10-20min, and cooling the cooling stirrer by water to reduce the temperature of the materials to below 50 ℃; discharging the materials, and pulverizing into granules in a pulverizer;

(10) and putting the crushed granular materials into a reactive extrusion process, further meshing, copolymerizing, plasticizing and reacting at high temperature by a double-screw extruder to obtain uniform materials, performing negative pressure devolatilization through a vacuum port to remove moisture and volatile substances, finally finishing extrusion of the zipper pulls, and packaging by using a tractor air-cooled reel.

4. The preparation process of the sheet-grade fully biodegradable polyester according to claim 3, wherein the degree of thinning of the corn starch and the stearic acid in the step (1) in the refiner is more than 1200 meshes.

Background

The twenty-first century is energy resource saving and ecological environment protection society, plastic is one of the most widely applied materials, and has been the first in the world by volume, the world plastic yield reaches 1.8 hundred million tons in 2020, and the plastic yield of China is about two thousand and more than ten thousand tons. The raw materials for plastics are derived from petroleum, and the demand for petroleum is enormous in order to meet such a huge production of plastics. Nowadays, global petroleum resources are in more and more shortage, and the demand of petroleum is more and more increased, so that the price of petroleum is increased dramatically, and further the price of plastic raw materials is increased dramatically.

Once the plastic is produced, the plastic is widely applied to a plurality of fields and becomes an indispensable part in our lives, but the application of the plastic promotes the development of industrial and agricultural production and simultaneously brings about a serious 'white pollution' problem. In particular to disposable plastic products mainly made of raw materials such as PE, PP and the like, which are usually discarded in every corner of our life after finishing certain functional purposes. As the proportion of plastic waste in the total amount of solid waste has increased year by year, such huge amounts of waste plastic dispersed in the environment have caused serious "white pollution", and the environmental pollution and the influence on living things caused by them have become a worldwide social problem. According to the research of scientists, a plastic bag can be completely degraded in about 1000 years, and because the degradation time of the plastic wastes is extremely long, the plastic bag causes a lot of damage and crisis to the living environment and the ecological environment of people.

In mountains, pastoral areas, rural areas, oceans and other places, the phenomenon of the non-degradable plastic products is normal, potential hazards are very large, the non-degradable plastic products enter soil and can influence the transfer of matters and heat in the soil and the growth of microorganisms, the characteristics of the soil are changed, after the non-degradable plastic products enter the soil, the waste plastic products can influence crops to absorb nutrients and moisture, for example, a plastic film exists in the field for a long time, the cultivation is prevented, the water-fertilizer and microorganism balance of the soil is damaged, and the adverse effect on the growth of the crops is caused. The plastic products discarded on the ground and in water are easily swallowed by animals as food, and the waste plastic products can not be digested in intestines and stomach of the animals, so that the animals are injured and killed.

In summary, the harm caused by the disposable plastic product waste is fully paid attention to the country, and the country has many defects that the used plastic is treated by methods such as burying, burning and recycling. The national development and transformation committee, the department of ecological environment and other nine departments jointly issue a notice about the work of strengthening and promoting plastic pollution control, and propose that from 1 month and 1 day of 2021, the use of non-degradable plastic lunch boxes and plastic shopping bags is forbidden in places such as markets, supermarkets, drug stores, bookstores and the like in built-up areas of direct municipalities, provincial cities and planned single-row cities, catering packaging take-out services and various exhibition activities. Therefore, a novel environment-friendly material which reduces the dependence on petroleum, has the same excellent service performance as common plastics and is completely degraded in the natural environment after being abandoned is needed to replace common petrochemical resin. Based on this, it is especially necessary to develop a sheet grade fully biodegradable polyester.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the sheet-grade fully biodegradable polyester which has the same physical property and mechanical property as common plastics, is completely degraded in natural environment, protects the environment, has low manufacturing cost and is easy to popularize and use.

In order to achieve the purpose, the invention is realized by the following technical scheme: a sheet-grade full-biodegradable polyester is composed of the following raw materials in parts by weight: 45% of corn starch, 20% of filler, 20% of polybutylene adipate-co-terephthalate PBAT 10%, 10% of polylactic acid PLA, 5% of plasticizer, 1% of compatilizer, 4% of stabilizer, 3% of dispersant, 0.02% of initiator and cross-linking agent, 1.97% of lubricant and 0.01% of chain extender; the filler adopts calcium carbonate, the plasticizer adopts glycerol, the compatilizer adopts maleic anhydride, the stabilizer adopts stearic acid, the dispersant adopts polyethylene wax, the initiator and the crosslinking agent adopt dicumyl peroxide (DCP), and the lubricant adopts white oil.

Preferably, the fineness of the calcium carbonate is more than 1500 meshes, and the calcium carbonate is used as a filler of the fully biodegradable polyester to enhance the strength of the degradable plastic product.

A preparation process of sheet-level full-biodegradable polyester comprises the following preparation steps:

(1) uniformly mixing corn starch and stearic acid, and putting the mixture into a refiner for refining;

(2) placing the refined starch into a high-temperature mixer according to the formula proportion, stirring for 10-15min, controlling the temperature at 100 ℃ and 110 ℃, and volatilizing the moisture in the starch;

(3) adding glycerol, stirring for 5min, and controlling the temperature at 120-;

(4) adding calcium carbonate, stirring for 1min to uniformly mix the calcium carbonate and the starch;

(5) adding maleic anhydride and stirring for 3min, and controlling the temperature at 120-130 ℃;

(6) adding polyethylene wax and stirring for 2min, and controlling the temperature at 120-130 ℃;

(7) adding polybutylene adipate-butylene terephthalate copolymer PBAT, polylactic acid PLA and a chain extender, stirring for 4min, and controlling the temperature at 130-150 ℃;

(8) adding dicumyl peroxide (DCP) and white oil, stirring for 2min, and controlling the temperature at 130-150 ℃;

(9) gradually agglomerating the materials along with the rise of the temperature of the materials, opening volatilization holes to fully volatilize water, opening a discharge valve when the material agglomerates are gradually dispersed, starting a cold pot to stir, slowly feeding the materials into the cold pot, immediately putting the materials into a cooling stirrer after the materials are modified in a high-speed mixing modification machine, stirring for 10-20min, and cooling the cooling stirrer by water to reduce the temperature of the materials to below 50 ℃; discharging the materials, and pulverizing into granules in a pulverizer;

(10) and putting the crushed granular materials into a reactive extrusion process, further meshing, copolymerizing, plasticizing and reacting at high temperature by a double-screw extruder to obtain uniform materials, performing negative pressure devolatilization through a vacuum port to remove moisture and volatile substances, finally finishing extrusion of the zipper pulls, and packaging by using a tractor air-cooled reel.

Preferably, in the step (1), the corn starch and the stearic acid are placed into a refiner for refining, and the refining degree is more than 1200 meshes.

The invention has the beneficial effects that: the fully biodegradable polyester prepared by the process has the same physical properties and mechanical properties as common plastics, can be completely degraded in natural environment, protects environment, is environment-friendly and energy-saving, reduces the dependence on petroleum, and has wide application prospect.

Drawings

The invention is described in detail below with reference to the drawings and the detailed description;

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

Referring to fig. 1, the following technical solutions are adopted in the present embodiment: a sheet-grade full-biodegradable polyester is composed of the following raw materials in parts by weight: 45% of corn starch, 20% of filler, 20% of polybutylene adipate-co-terephthalate PBAT 10%, 10% of polylactic acid PLA, 5% of plasticizer, 1% of compatilizer, 4% of stabilizer, 3% of dispersant, 0.02% of initiator and cross-linking agent, 1.97% of lubricant and 0.01% of chain extender; the filler adopts calcium carbonate, the plasticizer adopts glycerol, the compatilizer adopts maleic anhydride, the stabilizer adopts stearic acid, the dispersant adopts polyethylene wax, the initiator and the crosslinking agent adopt dicumyl peroxide (DCP), and the lubricant adopts white oil.

In the specific embodiment, corn starch, a filler (calcium carbonate), a butylene adipate-terephthalate copolymer (PBAT) and a polylactic acid (PLA) are used as main raw materials, a plasticizer (glycerol), a compatilizer (maleic anhydride), a stabilizer (stearic acid), a dispersant (polyethylene wax), an initiator, a cross-linking agent (dicumyl peroxide (DCP)), a lubricant (white oil) and a chain extender are used as auxiliary agents, the main raw materials are mixed at high temperature by a high-temperature mixer, the mixture is mixed by a double-screw extruder, and the extruded copolymer degrades a polyester sheet product, can be used for downstream product processing without adding any plastic, and specifically, the raw materials are described as follows:

(1) corn starch: the natural high molecular compound which is used as the main raw material of the full-biodegradable polyester and takes the corn starch as the raw material has sustainable supply, so that the natural resources can be repeatedly used and can replace plastic products taking petroleum as the raw material. The full-biodegradable polyester product taking the corn starch as the main raw material can be quickly degraded by microorganisms in the natural environment after the product is used to become plant nutrients, really comes from nature, effectively solves the environmental damage caused by white pollution in nature, and completely accords with the international environmental protection standard of 4R (low consumption, green material, recycling and reciprocating production) +1D (degradable).

(2) Calcium carbonate: as a filler of the full-biodegradable polyester, the fineness is more than 1500 meshes, and the filler has the characteristics of good dispersibility, high strength, good compatibility with a copolymer and low cost, and can enhance the strength of a degradable plastic product.

(3) Polybutylene adipate and terephthalate copolymer PBAT: the PBA and PBT have the characteristics of PBA and PBT, and have good ductility and elongation at break, and good heat resistance and impact resistance; in addition, PBAT is an excellent biodegradable material, can be used for improving the mechanical property of polylactic acid (PLA), is used as one of degradable plastic auxiliary materials, and improves the processing property, the ductility and the flexibility of a product.

(4) Polylactic acid PLA: as a novel bio-based and renewable biodegradable material, the biodegradable material is prepared by using renewable plant resources, such as starch raw materials proposed by corn, cassava and the like. The starch raw material is saccharified to obtain glucose, the glucose and certain strains are fermented to prepare high-purity lactic acid, and the polylactic acid with certain molecular weight is synthesized by a chemical synthesis method. PLA has good biodegradability, can be completely degraded by microorganisms in the nature under specific conditions after being used, finally generates carbon dioxide and water, does not pollute the environment, and is very favorable for protecting the environment. PLA is used as one of the degradable plastic auxiliary materials, and can improve the impact strength, the bending strength, the tensile strength and the like of the product.

(5) Glycerol: starch molecules have a large amount of-OH, adjacent molecules form strong crystallization through the-OH, and a large amount of molecular chains are gathered together to form a compact double-spiral structure, so that starch crystal particles have hard shells, the surface layers of the starch particles can only be treated by common chemical action, and the molecular chains in the starch particles cannot be broken up. When glycerin is used as a plasticizer and is mixed with a polymer, the temperature is raised, so that the thermal molecular motion of the polymer becomes violent, the acting force between chains is weakened, the distance between molecules is expanded, and the small molecular plasticizer is drilled between the chains of the macromolecular starch, so that the polar group of the plasticizer interacts with the polar group of the starch molecule to replace the polar action between the starch molecules, and the starch granules are swelled.

Meanwhile, the non-polar part in the plasticizer can shield the polar part of the starch molecules and increase the distance between the molecules, so that the van der Waals force between starch molecule chains is weakened, the molecular chains are easy to move, the melting temperature of the starch is reduced, and the starch is easy to process. The plasticized starch spherulites have small size and increased number of spherulites, the hydrogen bond function among starch molecules is weakened and destroyed, the diffusion capacity of molecular chains is improved, the glass transition temperature of the material is reduced, the microcrystalline melting of the starch before decomposition is realized, and the starch molecular chains are changed from double helix conformation to random coil conformation, so that the starch spherulites has the possibility of thermoplastic processing.

(6) Maleic anhydride: through esterification reaction, starch-OH is replaced by long chains, hydrogen bonds among starch molecules are greatly weakened, and macromolecules can move at a lower temperature, so that the aim of reducing the melting temperature is fulfilled. because-OH is replaced, the hydrophilicity of-OH is obviously weakened, the viscosity is reduced, the stability is improved, and the processability of degraded plastics is improved. Meanwhile, the formability is excellent, the formed material has flexibility and elasticity, and the ester bond is introduced, so that the compatibility of the material and other processing aids is improved.

(7) Stearic acid: the natural starch has the characteristics of high viscosity, poor fluidity and strong hydrophilicity, so that the starch needs to be modified by stearic acid, the starch has esterification by utilizing the dehydration and esterification reaction of the hydroxyl of the starch and the hydroxyl of the stearic acid and physical and chemical modification, and meanwhile, the hydrophobicity of the starch is increased, and the thermal stability is improved in the processing process of degrading plastics. Stearic acid has a plurality of hydroxyl groups, can effectively modify and disperse plastic fillers (calcium carbonate, talcum powder and starch), and can enter a double screw after being mixed with PBAT, so that the prepared plastic master batch or sheet has good internal and external lubricity.

(8) Polyethylene wax: the polyethylene wax has excellent external lubrication effect and strong internal lubrication effect, has the characteristic of good intermiscibility with polymers of PBAT and PLA, and can solve the problems of poor polymer fluidity and uneven mixing by adding the polyethylene wax when the polymers are mixed at high temperature. The polyethylene wax can be used as a lubricant in the processes of extrusion, calendering, injection and the like, can improve the processing efficiency, prevent and overcome sheet adhesion, and improve the processing performance, the surface gloss, the lubricating property and the thermal stability.

(9) Dicumyl peroxide DCP: because PBAT and PLA are incompatible materials, DCP is used as a cross-linking agent to modify the compatibility of PBAT and PLA, the function is that under a certain temperature, an initiator is decomposed to generate free active radicals, and the free active radicals initiate the chain end of PBAT to generate a chain leading reaction, so that starch or PBAT generates a grafting reaction to generate a substance with an interface enhancing function, the DCP can improve the tensile strength and the impact strength of the PBAT/PLA, starch and other copolymers, the addition of the DCP has a great promotion function on the crystallization rate of the PBAT/PLA and other materials, and the toughness and the heat resistance of the copolymer can be improved.

(10) White oil: the white oil has various effects in the actual processing of plastics, such as preventing polymers from sticking to a cylinder, inhibiting frictional heat generation, reducing mixing torque and load, and preventing thermal degradation of polymer materials during mixing and extrusion processing; during extrusion molding, the flowability can be improved, the adhesion of the polymer material with a charging barrel and a die can be improved, and retentate can be prevented and reduced; in addition, the appearance and gloss of the polymer material can be improved.

(11) Chain extender: the chain extender can improve the molecular weight of the polycondensate through reaction processing, adjust and control the intrinsic viscosity of the polyester plastic to recover and improve the mechanical property, the thermal property, the processing property and the optical balance, thereby providing higher melt strength, promoting the upgrading of the polycondensate with lower molecular weight, improving the compatibility of polycondensate alloy, improving the stability against hydrolysis and bringing higher processing flexibility for processing PLA, PBAT and other biodegradable polymers.

A preparation process of sheet-level full-biodegradable polyester comprises the following preparation steps:

uniformly mixing corn starch and stearic acid, and putting the mixture into a refiner for refining, wherein the refining degree is over 1200 meshes;

secondly, placing the refined starch into a high-temperature mixer according to the formula proportion, stirring for 10-15min, controlling the temperature at 110 ℃ and volatilizing the moisture in the starch;

adding glycerol and stirring for 5min, and controlling the temperature at 120-130 ℃;

adding calcium carbonate and stirring for 1min to uniformly mix the calcium carbonate and the starch;

adding maleic anhydride and stirring for 3min, and controlling the temperature at 120-130 ℃;

sixthly, adding polyethylene wax and stirring for 2min, and controlling the temperature at 120-130 ℃;

adding butanediol adipate and butanediol terephthalate copolymer PBAT, polylactic acid PLA and a chain extender, stirring for 4min, and controlling the temperature at 130-150 ℃;

adding dicumyl peroxide (DCP) and white oil, and stirring for 2min at the temperature of 130-150 ℃;

ninthly, gradually agglomerating the materials along with the rise of the temperature of the materials, opening a volatilization hole to fully volatilize moisture, opening a discharge valve when the material agglomerates are gradually dispersed, starting a cold pot to stir, slowly feeding the materials into the cold pot, immediately putting the materials into a cooling stirrer after the materials are modified in a high-speed mixing modification machine, stirring for 10-20min, and cooling the cooling stirrer by water to reduce the temperature of the materials to below 50 ℃; discharging the materials, and pulverizing into granules in a pulverizer;

and putting the crushed granular material into a reactive extrusion process at the salt part, further meshing, copolymerizing, plasticizing and reacting at high temperature by a double-screw extruder to obtain a uniform material, devolatilizing the uniform material through a vacuum port under negative pressure, removing moisture and volatile substances, finally finishing extrusion of the zipper pulls, and packaging the extruded zipper pulls by a tractor air-cooled reel.

The finished product prepared by the process is sheet type full-biodegradable polyester, and can be used for producing downstream products, such as: disposable lunch box, packing box, cup, plate, bowl, box, barrel, etc.

The specific embodiment adopts the production process of mixing raw materials at high temperature, mixing and modifying in a double-screw extruder, extruding sheets with various specifications in a sheet machine and molding and forming on a positive machine and a negative machine according to the requirements, so that the plasticizing process of the product is good and the process requirement is strict. The preparation process is based on the principle of graft polymerization reaction and blending modification of high molecular polymer, wherein the polymer graft polymerization reaction is that under the condition of a chemical initiator, chain segments of the high molecular polymer are initiated to generate an active center, and the active center directly reacts with other functional groups to form a graft polymer; blending and modification are substances in which two or more substances form a uniform phase by the action of strong shearing, kneading, and the like. Through the two functions, functional groups are introduced, the performance of the original material is kept, and a new material with a thermoplastic function is formed.

The copolymer is subjected to physical modification and chemical modification to form the thermoplastic full-biodegradable polyester, the thermoplastic full-biodegradable polyester accords with the national GB/T18006.3-2020 standard, has the same physical property and mechanical property as common plastics, has reproducibility, can be degraded in a short time in the natural environment, and has no pollution after degradation, so that the effects of reducing environmental pollution and relieving environmental contradiction are achieved, the environment friendliness is good, the requirements of reduction, reclamation and harmlessness in the national solid waste pollution prevention and control law are met, and the thermoplastic full-biodegradable polyester has a wide market application prospect.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.