阅读说明：本技术 一种低成本快速降解的农用塑料地膜及制备方法 (Low-cost and quick-degradation agricultural plastic mulching film and preparation method thereof ) 是由 陈庆 曾军堂 于 2019-09-27 设计创作，主要内容包括：本发明提出一种低成本快速降解的农用塑料地膜及制备方法,所述塑料地膜是以酯化淀粉糊、微细改性木质粉、交联剂、无机填料、助膜剂组成的浆料为原料,在转动的辊筒表面附着并热固化干燥成膜,定型、卷取而制得；所述酯化淀粉糊是淀粉、酯化剂、淀粉酶分散于水中后,淀粉在糊化过程中酯化改性而制得；所述微细改性木质粉是粉碎的木质物与硬脂酸在气流粉碎机中细化分散而制得。本发明的原料价廉易得、生产设备简单、制备方法简单易操作,产品稳定性良好,制得的农用塑料地膜,具有优异的保水、保湿效果,且在一年内完全降解,不会导致土壤板结,膜幅宽可根据辊筒大小任意调节,为规模化推广生物塑料在农用地膜的应用提供了可靠的技术支撑。(The invention provides an agricultural plastic mulching film with low cost and rapid degradation and a preparation method thereof, wherein the plastic mulching film is prepared by taking slurry consisting of esterified starch paste, micro-fine modified wood powder, a cross-linking agent, an inorganic filler and an auxiliary film agent as raw materials, adhering to the surface of a rotating roller, performing thermosetting drying to form a film, shaping and coiling; the esterified starch paste is prepared by dispersing starch, an esterifying agent and amylase in water and then esterifying and modifying the starch in the gelatinization process; the fine modified wood powder is prepared by thinning and dispersing crushed wood and stearic acid in a jet mill. The raw materials are cheap and easy to obtain, the production equipment is simple, the preparation method is simple and easy to operate, the product stability is good, the prepared agricultural plastic mulching film has excellent water retention and moisture retention effects, is completely degraded within one year, does not cause soil hardening, can be adjusted freely according to the size of the roller, and provides reliable technical support for large-scale popularization of application of bioplastic in agricultural mulching films.)

1. An agricultural plastic mulching film with low cost and rapid degradation is characterized in that the plastic mulching film is prepared by adhering slurry consisting of esterified starch paste, micro-fine modified wood powder, a cross-linking agent, an inorganic filler and an auxiliary film agent on the surface of a rotating roller, thermally curing, drying, forming a film, shaping and coiling; the esterified starch paste is prepared by dispersing starch, an esterifying agent and amylase in water and then esterifying and modifying the starch in the gelatinization process; the fine modified wood powder is prepared by thinning and dispersing crushed wood and stearic acid in a jet mill, and is prepared by the following method:

(1) crushing the wood, adding stearic acid, and performing thinning dispersion in a jet mill until the particle size is less than 10 microns to obtain fine modified wood powder; the mass proportion of the wood substance to the stearic acid is 100: 3-6;

(2) adding starch, esterifying agent and amylase into water, stirring and gelatinizing at 60-80 deg.C, reducing crystallinity of starch under the action of amylase and temperature, and modifying by esterifying agent to obtain water-resistant esterified starch paste; the mass mixing ratio of the starch, the esterifying agent, the amylase and the water is 100:3-5:0.01-0.02: 300-350;

(3) uniformly dispersing the esterified starch paste, the fine modified wood powder, the cross-linking agent, the inorganic filler and the film aid agent to prepare slurry; the mass mixing ratio of the esterified starch paste to the fine modified wood powder, the cross-linking agent, the inorganic filler and the film aid agent is 100:10-20:0.5-1:5-10: 20-30;

(4) and transferring the slurry into a slurry tank, maintaining the temperature at 40-60 ℃, arranging a rotary high-temperature roller at the upper part of the charging tank, adhering a layer of slurry on the surface of the roller when the roller slowly rotates, carrying out thermocuring and drying to form a film, continuously uncovering the film, sending the film into three groups of shaping press rollers for shaping, and reeling in reeling rollers to obtain the low-cost and rapidly-degradable agricultural plastic mulching film.

2. The low-cost rapidly-degradable agricultural plastic mulching film according to claim 1, wherein the cross-linking agent is one or a combination of more than two of borax, sodium metaphosphate and sodium tripolyphosphate.

3. The low-cost rapidly-degradable agricultural plastic mulching film according to claim 1, wherein the inorganic filler is one or a combination of more than two of talcum powder, calcium carbonate powder and bentonite powder.

4. The low-cost rapidly-degradable agricultural plastic mulching film according to claim 1, wherein the filming aid agent is an acrylic emulsion, and the solid content is 40 ± 1%.

5. The low-cost rapidly-degradable agricultural plastic mulching film according to claim 1, wherein the starch is one or both of tapioca starch and corn starch.

6. The low-cost rapidly degradable agricultural plastic mulching film according to claim 1, wherein the esterifying agent is one or a combination of two or more of stearic acid, lauric acid, myristic acid, palmitic acid, oleic acid and linoleic acid.

7. The low-cost rapidly-degradable agricultural plastic mulching film according to claim 1, wherein the wood material is one or a combination of more than two of straw powder, fallen leaves and sawdust.

8. The preparation method of the low-cost quick-degradation agricultural plastic mulching film according to any one of claims 1 to 7, which is characterized by comprising the following steps of:

(1) crushing the wood, adding stearic acid, and performing thinning dispersion in a jet mill until the particle size is less than 10 microns to obtain fine modified wood powder; the mass proportion of the wood substance to the stearic acid is 100: 3-6;

(2) adding starch, esterifying agent and amylase into water, stirring and gelatinizing at 60-80 deg.C, reducing crystallinity of starch under the action of amylase and temperature, and modifying by esterifying agent to obtain water-resistant esterified starch paste; the mass mixing ratio of the starch, the esterifying agent, the amylase and the water is 100:3-5:0.01-0.02: 300-350;

(3) uniformly dispersing the esterified starch paste, the fine modified wood powder, the cross-linking agent, the inorganic filler and the film aid agent to prepare slurry; the mass mixing ratio of the esterified starch paste to the fine modified wood powder, the cross-linking agent, the inorganic filler and the film aid agent is 100:10-20:0.5-1:5-10: 20-30;

(4) and transferring the slurry into a slurry tank, maintaining the temperature at 40-60 ℃, arranging a rotary high-temperature roller at the upper part of the charging tank, adhering a layer of slurry on the surface of the roller when the roller slowly rotates, carrying out thermocuring and drying to form a film, continuously uncovering the film, sending the film into three groups of shaping press rollers for shaping, and reeling in reeling rollers to obtain the low-cost and rapidly-degradable agricultural plastic mulching film.

9. The method for preparing an agricultural plastic mulching film with low cost and rapid degradation according to claim 8, wherein the jet pressure of the jet milling in the step (1) is 0.8-1.2MPa, and the dispersion time is 20-30 s.

10. The method for preparing an agricultural plastic mulching film with low cost and rapid degradation as claimed in claim 8, wherein the temperature of the roller of the high temperature roller in the step (4) is set to be 100 ℃ and 120 ℃, and the linear speed of rotation is 20-30 cm/s.

Technical Field

The invention relates to the technical field of preparation of degradable materials, in particular to an agricultural plastic mulching film capable of being rapidly degraded at low cost and a preparation method thereof.

Background

White pollution refers to waste plastics, such as plastic bags, foam boards and the like which are most common in our daily life, and the waste plastics are not easy to degrade and can be decomposed for hundreds of years. The hazards they cause are as follows: the city appearance environment is damaged, the abandoned plastic products are visible everywhere, which is an important reason for dirtiness, disorder and poor environment, the landscape is also damaged, and the city image is influenced; the plastic products which are abandoned, if being adhered with pollutants, can become a hotbed for the survival and the propagation of mosquitoes and flies and bacteria, thus being harmful to the human health; the growth of crops is influenced, and after the plastic film used in the farmland is aged, the plastic film can be broken and left in the farmland, is not decomposed and rotted, destroys the land structure, prevents the plants from absorbing water and the roots from growing, and influences the harvest of the crops; the safety of animals is endangered, and waste plastic fragments scattered in rivers, lakes, seas and fields are eaten by animals and small organisms by mistake, so that the animals and the small organisms can be ill and die.

China is a large population country, the quantity of needed agricultural products is large, and the development and application of the mulching film technology greatly promote the development of agriculture and the improvement of crop yield in China. The plastic mulching film has simple process, wide and cheap raw materials, and has the functions of moisturizing and heat preservation, and is used in large quantity to be beneficial to the growth and development of crops and improve the yield and economic benefit of the crops. The application of plastic mulching films in a large amount also causes a large amount of white pollution, and the undegraded plastic can cause the problems of soil hardening, poor air permeability, land capability reduction and the like, thereby influencing the growth, development and yield of crops.

The biodegradable plastic is beneficial to saving resources and reducing environmental load; the treatment of the waste can adopt composting treatment, can realize resource recycling, meets the requirement of sustainable development, and is imperative to research biodegradable plastics along with the increasing aggravation of environmental problems. Particularly, with the rising of the development and the promotion of rural areas, the plastic mulching film is applied to various paddy fields and dry lands, and how to ensure the rapid degradation of the plastic mulching film becomes a key point.

According to the prior art, the biodegradable plastics comprise polylactic acid (PLA), polybutylene succinate (PBS), carbon dioxide polymer (PPC), Polycaprolactone (PCL), Polyhydroxyalkanoate (PHA) and the like, but the biodegradable plastics are generally high in cost, long in degradation period and difficult to popularize and apply in a large area.

The Chinese patent application No. 201110354439.0 discloses an environment-friendly controllable degradation agricultural mulching film, which is prepared by the following raw materials in parts by weight through melt blending, extrusion and film blowing: 25-50 parts of polyvinyl alcohol, 72-87 parts of starch, 10-20 parts of micromolecule plasticizer, 0.2-2 parts of modified inorganic nano-additive, 0.5-1.5 parts of antioxidant, 0.5-1.5 parts of compatibilizer and 0.2-1.5 parts of ultraviolet absorbent. The Chinese patent application No. 201810820912.1 discloses a biodegradable plastic film, which is prepared from the following raw materials in parts by weight: 70-80 parts of linear low-density polyethylene, 10-20 parts of corn starch, 8-12 parts of plant fiber, 0.5-1.5 parts of compatilizer, 1-2 parts of coupling agent, 1-2 parts of dispersing agent and 1-2 parts of degrading agent.

In order to shorten the degradation period of the agricultural plastic mulching film, reduce the cost and reduce the processing difficulty, a new plastic mulching film and a preparation method thereof need to be provided, and further reliable technical support is provided for the application of the biological plastic mulching film.

Disclosure of Invention

Aiming at the defects of high cost, large difficulty in film forming and long degradation period of the existing biodegradable plastic, the invention provides the agricultural plastic mulching film with low cost and rapid degradation and the preparation method thereof, which can reduce the cost of the mulching film, facilitate film forming and ensure rapid degradation of the mulching film within one year.

In order to solve the problems, the invention adopts the following technical scheme:

an agricultural plastic mulching film with low cost and rapid degradation is prepared by adhering slurry consisting of esterified starch paste, micro-fine modified wood powder, a cross-linking agent, an inorganic filler and an auxiliary film agent on the surface of a rotating roller, thermally curing, drying, forming a film, shaping and coiling; the esterified starch paste is prepared by dispersing starch, an esterifying agent and amylase in water and then esterifying and modifying the starch in the gelatinization process; the fine modified wood powder is prepared by thinning and dispersing crushed wood and stearic acid in a jet mill.

Preferably, the cross-linking agent is one or a combination of more than two of borax, sodium metaphosphate and sodium tripolyphosphate.

Preferably, the inorganic filler is one or a combination of more than two of talcum powder, calcium carbonate powder and bentonite powder.

Preferably, the filming aid is acrylic emulsion, and the solid content is 40 +/-1%.

Preferably, the starch is one or two of tapioca starch and corn starch.

Preferably, the esterification agent is one or a combination of more than two of stearic acid, lauric acid, myristic acid, palmitic acid, oleic acid and linoleic acid.

Preferably, the wood material is one or a combination of more than two of straw powder, fallen leaves and sawdust.

The invention also provides a preparation method of the low-cost and quick-degradation agricultural plastic mulching film, which comprises the following steps:

(1) crushing the wood, adding stearic acid, and performing thinning dispersion in a jet mill until the particle size is less than 10 microns to obtain fine modified wood powder; the mass proportion of the wood substance to the stearic acid is 100: 3-6;

(2) adding starch, esterifying agent and amylase into water, stirring and gelatinizing at 60-80 deg.C, reducing crystallinity of starch under the action of amylase and temperature, and modifying by esterifying agent to obtain water-resistant esterified starch paste; the mass mixing ratio of the starch, the esterifying agent, the amylase and the water is 100:3-5:0.01-0.02: 300-350;

(3) uniformly dispersing the esterified starch paste, the fine modified wood powder, the cross-linking agent, the inorganic filler and the film aid agent to prepare slurry; the mass mixing ratio of the esterified starch paste to the fine modified wood powder, the cross-linking agent, the inorganic filler and the film aid agent is 100:10-20:0.5-1:5-10: 20-30;

(4) and transferring the slurry into a slurry tank, maintaining the temperature at 40-60 ℃, arranging a rotary high-temperature roller at the upper part of the charging tank, adhering a layer of slurry on the surface of the roller when the roller slowly rotates, carrying out thermocuring and drying to form a film, continuously uncovering the film, sending the film into three groups of shaping press rollers for shaping, and reeling in reeling rollers to obtain the low-cost and rapidly-degradable agricultural plastic mulching film.

Preferably, the jet pressure of the jet milling in the step (1) is 0.8-1.2MPa, and the dispersion time is 20-30 s.

Preferably, the roller temperature of the high-temperature roller in the step (4) is set to be 100-120 ℃, and the rotating linear speed is 20-30 cm/s.

It is known that starch has good biodegradability. Starch molecules contain a large amount of hydroxyl groups, the interaction force among macromolecules is strong, the melt processing is difficult, the hydroxyl groups can generate chemical reactions such as esterification, etherification, grafting, crosslinking and the like, the chemical reactions are utilized to modify the starch, the hydroxyl groups are reduced, the original structure is changed, and thus the original starch is converted into thermoplastic starch, which is beneficial to the processing of starch products; on the other hand, the starch has a semi-crystalline particle structure, wherein one part of molecules in the particles are arranged into a loose amorphous region (amorphous region), the other part of molecules are arranged into a highly ordered crystalline region, and the crystalline region is very firm, has strong resistance to water, enzymes and chemical reagents, hinders the degradation of the starch, modifies the starch, improves the reactivity of the starch molecules, and is beneficial to accelerating the degradation process of the starch. The invention adopts amylase to gelatinize starch and uses esterifying agent to esterify and modify, thus improving the processability and degradation speed of starch.

Furthermore, the cross-linking agent is added into the starch slurry, so that the water resistance of the mulching film is improved. The crosslinking agent is generally a substance having a plurality of functional groups in a molecule or a compound having a plurality of unsaturated double bonds in a molecule, and is mainly used in a polymer material. Because the molecular structure of the high polymer material is like a long line, the high polymer material has low strength when not crosslinked, is easy to break, has no elasticity and is easy to be corroded by external water. The function of the cross-linking agent is to generate chemical bonds between linear molecules, so that the linear molecules are connected with each other to form a network structure. And a cross-linking agent is added into the slurry to further cross-link starch molecules, which is beneficial to improving the water resistance after film formation.

Furthermore, the invention adopts a method of continuously forming the film by a high-temperature roller, the esterified starch paste is coated with wood powder and inorganic powder, and the film is formed by passing through the high-temperature roller rotating at a low speed and thermally drying and curing under the assistance of the acrylic emulsion, and the film forming process is continuous. By adjusting the size of the roller, plastic films with different widths can be obtained. Moreover, compared with the film forming method of blowing film forming and rolling film forming, the film forming method has the advantages of low requirement on raw materials, low cost, no need of screw extrusion granulation, and capability of preparing the biological material with poor heat resistance into a film.

The existing agricultural degradable mulching film adopts polylactic acid (PLA), polybutylene succinate (PBS), carbon dioxide polymer (PPC), Polycaprolactone (PCL), Polyhydroxyalkanoate (PHA) and the like, and has the defects of high processing difficulty, high cost and long degradation period. In view of the above, the invention provides an agricultural plastic mulching film with low cost and rapid degradation, wherein stearic acid is adopted in a jet mill to carry out fine modification on a wood substance under the air flow pressure of 0.8-1.2MPa, so as to obtain fine modified wood powder with the particle size of less than 10 microns; then gelatinizing and esterifying the plant starch by using an esterifying agent and amylase at the temperature of 60-80 ℃ to obtain esterified starch paste; then uniformly dispersing the esterified starch paste, the micro-fine modified wood powder, the cross-linking agent, the inorganic filler and the film aid agent to prepare slurry; further carrying out thermosetting drying on the slurry through a high-temperature roller at the temperature of 100-120 ℃ to form a film, and carrying out continuous film uncovering, compression roller sizing and coiling to obtain the low-cost and rapidly-degradable agricultural plastic mulching film. The raw materials are cheap and easy to obtain, the production equipment is simple, the preparation method is simple and easy to operate, the product stability is good, the prepared agricultural plastic mulching film has excellent water retention and moisture retention effects, can be completely degraded within one year, cannot cause soil hardening, and the film width can be adjusted at will according to the size of the roller.

Compared with the prior art, the invention provides the low-cost and fast-degradation agricultural plastic mulching film and the preparation method thereof, and the outstanding characteristics and excellent effects are as follows:

1. according to the preparation method, the starch is prepared into a paste shape, then the paste is coated with the wood powder and the inorganic powder, and the film is formed under the acrylic emulsion auxiliary film through thermal drying and curing, so that the process of forming the film is continuous, the large-scale production is easy, the production equipment is simple, and the width of the film can be adjusted freely according to the size of the roller.

2. The preparation method of the invention does not need screw extrusion granulation, overcomes the problem that the existing bioplastic material has poor heat resistance and is difficult to be processed by thermoplastic molding, and provides reliable technical support for large-scale popularization of the application of bioplastic in agricultural mulching films.

3. The mulching film prepared by the invention has excellent water retention and moisture retention effects, can be completely degraded within one year, cannot cause soil hardening, and has both environmental protection and economy.

Drawings

FIG. 1: the invention step (4) utilizes the roller surface to dip-dye the sizing agent and heat-cure and dry the process schematic diagram of the film, wherein, 1-sizing agent pool; 2-high temperature roller; 3-shaping press rolls; 4-a winding roller;

FIG. 2: the natural disintegration pattern of the agricultural mulching film obtained in example 1 after 4 months of natural light irradiation.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.