Straw paper mulching film based on thermo-mechanical pulp as well as green preparation method and application of straw paper mulching film

Abstract

The invention discloses a straw paper mulching film based on thermo-mechanical pulp as well as a green preparation method and application of the straw paper mulching film. The invention belongs to the field of biomass resource utilization. Aiming at the defects in the prior art, the invention provides a green preparation method of a straw paper mulching film based on thermo-mechanical pulp. According to the method, the staged hydrothermal grinding technology is adopted, washing is not needed, the acidic paper pulp is directly obtained, and the technological process is simplified. Meanwhile, the invention innovatively develops a green sizing agent taking chitosan as a main material. The sizing agent can be directly fused with acidic paper pulp, and acid and alkali do not need to be additionally added for adjusting the pH value. The dry tensile index of the straw paper mulching film is larger than or equal to 15 N.m / g, the wet tensile index is larger than or equal to 5 N.m / g, the burst index is larger than or equal to 3.5 kPa.m < 2 > / g, the contact angle is larger than or equal to 105 degrees, and the 2-hour water absorption rate is smaller than or equal to 50%.

Description

Technical Field

[0001] The present invention belongs to the field of biomass resource utilization, and particularly relates to a straw paper mulch film based on thermomechanical pulp, a green preparation method thereof and an application thereof. Background Art

[0002] The plastic film mulching technology is widely used in modern agriculture, and its main functions include warming and moisturizing the soil, promoting the growth of crops and increasing the yield. However, the currently widely used plastic mulch films cause serious environmental and soil pollution problems. The long-term use of plastic mulch films will lead to soil compaction, and the residues are difficult to degrade, causing irreversible damage to the ecological environment. The non-degradability of plastic mulch films causes them to accumulate in the soil, affecting the soil structure and microbial activities, and further affecting the growth of crops and soil health.

[0003] Although certain progress has been made in the research and development of degradable mulch films, the content of degradable mulch films on the current market is still less than 1%. This is mainly because the production cost of degradable mulch films is relatively high, and their performance is difficult to completely replace that of traditional plastic mulch films. In addition, the degradation rate and conditions of degradable mulch films are also difficult to control, resulting in unstable effects in actual applications. The raw materials used for degradable mulch films on the current market are limited, and most of them are not fully degradable. This means that even though the mulch films can be degraded to a certain extent, some residues will still be left, and these residues will still have a certain impact on the soil and the environment. This characteristic of partial degradation limits the wide application and popularization of degradable mulch films.

[0004] In recent years, degradable mulch films made of plant fibers as raw materials have gradually become a research hotspot. Plant fibers have the advantages of being renewable, degradable and environmentally friendly, and are ideal raw materials for mulch films. Among them, straw, as an abundant agricultural waste with an annual output of more than 900 million tons, has the characteristics of wide sources and low cost, and is an ideal raw material for pulp. Straw paper mulch films have gradually become a research hotspot due to their degradability, soil improvement characteristics and environmental friendliness. Straw paper mulch films not only have the characteristic of full degradation, but also have rich raw materials and low cost. The utilization of straw can not only reduce the environmental pollution of agricultural waste, but also improve the resource utilization rate. However, the industrialization of straw paper mulch films still faces many bottlenecks, mainly including problems such as low fiber separation efficiency, poor environmental compatibility of sizing agents and insufficient mechanical properties of paper mulch films.

[0005] Traditional methods for preparing pulp fibers usually require the use of strong acids or alkalis, resulting in severe fiber damage, with a chemical oxygen demand (COD) value as high as 5000 - 8000 mg / L and a 20% - 40% increase in treatment costs. This not only limits the green production of straw paper mulch films but also increases their economic costs. In addition, traditional sizing agents (such as alkyl ketene dimer, polyamide polyepichlorohydrin resin) are difficult to degrade, and the inhibition rate of the residues on the soil microbial community can reach 15% - 25%. Long-term use may cause soil compaction, further exacerbating the deterioration of the soil ecosystem.

[0006] Preparing paper mulch films with thermomechanical pulp is a method to solve the above problems. Through hydrothermal grinding technology, efficient separation of straw fibers can be achieved. The paper mulch films prepared with thermomechanical pulp do not add acids or alkalis, so no black liquor is produced, avoiding the high-COD wastewater generated in the traditional pulping process. This not only reduces environmental pollution but also lowers the cost of wastewater treatment. Although the paper mulch films prepared with thermomechanical pulp have environmental protection advantages, their film-forming mechanical properties are relatively low, and the tensile strength is generally lower than 30 N·m / g, which will cause the film material to break easily during mechanical film covering and poor adaptability to field operations; the wet strength is less than 5 N·m / g, which makes the mulch film soften and disintegrate prematurely in a humid environment, losing its functions of heat preservation and moisture retention, resulting in fluctuations in the growth environment of crops and out-of-control weeds. In order to improve the mechanical properties of paper mulch films, additives are usually needed. However, traditional additives (such as alkyl ketene dimer, polyamide polyepichlorohydrin resin) are not environmentally friendly, and the residues have an inhibitory effect on the soil microbial community. Therefore, it is particularly necessary to develop a green preparation method for high-performance paper mulch films. Summary of the Invention

[0007] In order to overcome the above technical defects, the present invention provides a straw paper mulch film based on thermomechanical pulp, its green preparation method and application.

[0008] The technical solution of the present invention is as follows:

[0009] One of the purposes of the present invention is to provide a green preparation method for a straw paper mulch film based on thermomechanical pulp, and the method is carried out according to the following steps:

[0010] Step 1: Place the straw in a hydrothermal reactor, add water to submerge the straw, perform hydrothermal treatment and then separate the solid and liquid. The obtained solid is mechanically ground to a fiber length of 0.8 - 1.2 mm;

[0011] Step 2: Re-place the straw fibers in the hydrothermal reactor, add water, and perform secondary hydrothermal treatment at high temperature. After hydrothermal treatment, grind again to a fiber length of 0.6 - 0.8 mm to obtain an acidic fiber slurry;

[0012] Step 3: Using the wash-free pulp technology, adding chitosan and epoxy-modified vegetable oil as a composite sizing agent, and then forming through a paper machine. After drying, the straw paper mulch film is obtained.

[0013] Further defined, the straw in Step 1 includes rice straw, corn straw, cotton stalks, and hemp stalks.

[0014] Further defined, the hydrothermal treatment temperature in Step 1 is 80 - 100 °C, and the time is 1 - 2 h.

[0015] Further defined, the secondary hydrothermal treatment temperature in Step 2 is 180 - 220 °C, and the time is 10 - 20 min.

[0016] Further defined, the pH value of the acidic fiber slurry in Step 2 is 4 - 5.

[0017] Further defined, the deacetylation degree of chitosan in Step 3 is ≥85%.

[0018] Further defined, the iodine value of the epoxy-modified vegetable oil in Step 3 is 90 - 110 g I2 / 100 g.

[0019] Further defined, the addition amount of chitosan in Step 3 is 2 - 3% of the dry weight of the pulp, and the addition amount of the epoxy-modified vegetable oil is 1 - 2% of the dry weight of the pulp.

[0020] The second object of the present invention is to provide a straw paper mulch film prepared by the above method, wherein the dry tensile index of the straw paper mulch film is ≥15 N·m / g, the wet tensile index is ≥5 N·m / g, the burst resistance index is ≥3.5 kPa·m 2 / g, the contact angle is ≥105°, and the water absorption rate within 2 hours is ≤50%.

[0021] The third object of the present invention is to provide an application of the straw paper mulch film prepared by the above method in the agricultural field.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] Through the innovative staged hydrothermal coupling hydro-grinding process and the application of the chitosan-vegetable oil composite sizing agent, the present invention realizes the efficient and green manufacturing of the straw paper mulch film, further reduces the production cost, and significantly improves the performance and environmental friendliness of the product. The specific invention effects are as follows:

[0024] (1) The present invention realizes the efficient separation of straw fibers through a staged hydrothermal grinding technique, while avoiding water resource waste and environmental pollution caused by multiple washings. First, through the mild hydrothermal conditions of preliminary hydrothermal treatment, the lignin in the straw is preliminarily softened, and at the same time, some impurities are separated, creating favorable conditions for subsequent fiber separation. On this basis, through mechanical grinding, the fibers are further refined, improving the flexibility and dispersibility of the fibers, and laying a foundation for subsequent fiber fibrillation treatment. Most importantly, the present invention adopts the synergistic effect of high-temperature hydrothermal and mechanical grinding to further promote fiber fibrillation. The cavitation effect significantly improves the degree of microfibrillation of the fibers. After treatment, the length distribution of the pulp fibers is 0.6 - 0.8 nm, the width range is 24 - 26 μm, the fibrillation rate is increased to 20% - 25%, and the specific surface area of the fibers is increased by 40 - 60%. This process improves the fiber utilization rate while effectively reducing energy consumption and raw material loss in the production process. And it significantly improves the physical properties of the fibers, enhancing the interweaving ability between the fibers, providing guarantee for the high-strength forming of the paper mulch film.

[0025] (2) The present invention adopts an in-situ regulation technique, enabling the slurry system to naturally form a slightly acidic environment with a pH of 4 - 5 after hydrothermal reaction without introducing an external pH regulator, and directly entering the sizing process. This process omits the traditional water washing step, simplifies the process flow, reduces the process water consumption by more than 30%, and avoids the problem of secondary wastewater treatment.

[0026] (3) The present invention innovatively develops a green sizing agent mainly made of chitosan. Chitosan and acidic pulp are tightly combined through electrostatic self-assembly effect and self-assemble into a film in the pulp, without the need for external acid activation. This not only reduces the use of chemical reagents, but also improves the sizing efficiency, uniformity, water resistance and wet strength of the paper mulch film. At the same time, by adding epoxy-modified vegetable oil to form a chitosan-vegetable oil composite sizing agent, the adhesion of the sizing agent and the mechanical properties of the paper mulch film are further enhanced.

[0027] (4) The performance indicators of the straw paper mulch film of the present invention are significantly improved:

[0028] Mechanical properties: The dry tensile index of the formed paper ≥ 15 N·m / g, the wet tensile index ≥ 5 N·m / g, and the burst resistance index ≥ 3.5 kPa·m 2 / g. These performance indicators are significantly better than those of traditional straw paper mulch films and can meet the requirements of wind resistance and soil covering in farmland.

[0029] Water resistance: The contact angle of the paper mulch film ≥ 105°, and the water absorption rate within 2 hours ≤ 50%. This performance optimization enables it to effectively prevent water penetration and maintain soil humidity during farmland use.

[0030] (5) The method of the present invention has environmental protection and economy:

[0031] Green manufacturing: No strong acids, strong bases or chemical modifiers are added during the entire process, reducing wastewater discharge and chemical oxygen demand (COD), which conforms to the concept of green manufacturing.

[0032] Cost reduction: By increasing the pulp yield and simplifying the process flow, the present invention significantly reduces the production cost and improves the market competitiveness of straw paper mulch film.

[0033] In summary, through process innovation and sizing agent adaptation, the present invention realizes the efficient and green manufacturing of straw paper mulch film, and has made remarkable improvements in mechanical properties, water resistance and degradability, providing strong support for the high-value utilization and sustainable development of agricultural waste. Description of the Drawings

[0034] Figure 1 Comparison of the dry tensile strength performance of the paper mulch film for Examples 1-4 and Comparative Example 2;

[0035] Figure 2 Comparison of the wet tensile strength performance of the paper mulch film for Examples 1-4 and Comparative Example 2;

[0036] Figure 3 Comparison of the bursting strength performance of the paper mulch film for Examples 1-4 and Comparative Example 2;

[0037] Figure 4 Physical diagram of the straw paper mulch film obtained in Example 2;

[0038] Figure 5 SEM image of the straw paper mulch film obtained in Example 2;

[0039] Figure 6 Diagram of the pulp example in Example 2. Detailed Description of the Invention

[0040] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, and those skilled in the art can obtain them through commercial channels without special instructions.

[0042] Example 1

[0043] The green preparation method of the rice straw paper mulch film based on thermomechanical pulp in this example is carried out according to the following steps:

[0044] (1) Raw material preparation

[0045] Select dry rice straw as raw material, cut it into small sections with a length of 5 cm, wash it clean and set aside.

[0046] (2) Preliminary hydrothermal treatment

[0047] Put the rice straw into a hydrothermal reactor, add water according to a liquid-solid ratio of 10:1, control the temperature at 80 °C, and the treatment time is 1.5 h. The main purpose of this stage is to soften lignin and separate impurities.

[0048] (3) Solid-liquid separation and hydro-grinding

[0049] Perform solid-liquid separation on the treated straw to remove the waste liquid. Subsequently, put the straw fibers into a hydro-grinder and grind them until the fiber length is 1.0 mm. Observe the flexibility and dispersibility of the fibers through a microscope to ensure that the fibers reach an ideal state.

[0050] (4) Secondary high-temperature hydrothermal coupling grinding treatment

[0051] Put the ground straw fibers back into the hydrothermal reactor, add water according to a liquid-solid ratio of 10:1, control the temperature at 200 °C, perform secondary hydrothermal treatment, and the treatment time is 10 min. After the hydrothermal treatment, start the grinding device until the fiber length is 0.7 mm to further fibrillation the fibers at high temperature.

[0052] (5) Sizing and sizing of the wash-free pulp

[0053] The treated acidic fiber slurry (pH 4.5) does not need to be washed. Add chitosan (degree of deacetylation ≥ 85%) and epoxy-modified vegetable oil (iodine value 100 g I2 / 100 g) to the slurry. The addition amount of chitosan is 3% of the pulp dry weight, and the addition amount of epoxy-modified vegetable oil is 2% of the pulp dry weight. After stirring evenly, chitosan and acidic pulp form a uniform sizing layer through the electrostatic self-assembly effect.

[0054] (6) Molding and drying of the paper mulch

[0055] Form the sized slurry through a paper machine, and control the thickness of the paper mulch to be 0.15 mm. The formed paper mulch is dried at 60 °C for 2 h to remove excess moisture, and finally the rice straw paper mulch is obtained.

[0056] Mechanical properties: Tested with a universal material testing machine, the dry tensile index is 16 N·m / g, and the wet tensile index is 5 N·m / g; the burst resistance index is 3.8 kPa·m 2 / g.

[0057] Water resistance: Tested with a contact angle measuring instrument, the contact angle is 108°, and the water absorption rate in 2 hours is 45%.

[0058] Example 2:

[0059] The green preparation method of corn straw paper mulch film based on thermomechanical pulp is carried out according to the following steps:

[0060] (1) Raw material preparation

[0061] Select dry corn straw as the raw material, cut it into small sections with a length of 5 cm, wash it clean and set aside.

[0062] (2) Preliminary hydrothermal treatment

[0063] Put the corn straw into a hydrothermal reactor, add water according to a liquid-solid ratio of 12:1, control the temperature at 85 °C, and the treatment time is 2 h. The main purpose of this stage is to soften lignin and separate impurities.

[0064] (3) Solid-liquid separation and hydrogrinding

[0065] Perform solid-liquid separation on the treated straw to remove the waste liquid. Subsequently, put the straw fibers into a hydrogrinder and grind them until the fiber length is 0.9 mm. Observe the flexibility and dispersibility of the fibers through a microscope to ensure that the fibers reach an ideal state.

[0066] (4) Secondary hydrothermal coupling grinding treatment

[0067] Put the ground fibers back into the hydrothermal reactor, add water according to a liquid-solid ratio of 10:1, control the temperature at 190 °C, perform secondary hydrothermal treatment, and the treatment time is 15 min. After the hydrothermal treatment, start the grinding device until the fiber length is 0.7 mm to further fibrillation the fibers at high temperature.

[0068] (5) Pulp washing, sizing and sizing

[0069] The treated acidic fiber pulp (pH 4.2) does not need to be washed. Add chitosan (deacetylation degree ≥ 85%) and epoxy modified vegetable oil (iodine value 95 g I2 / 100 g) to the pulp. The addition amount of chitosan is 2.5% of the dry weight of the pulp, and the addition amount of epoxy modified vegetable oil is 1.5% of the dry weight of the pulp. After stirring evenly, chitosan and acidic pulp form a uniform sizing layer through electrostatic self-assembly effect.

[0070] (6) Paper mulch film forming and drying

[0071] Form the sized pulp through a paper machine, and control the thickness of the paper mulch film to be 0.18 mm. The formed paper mulch film is dried at 65 °C for 1.5 h to remove excess moisture, and finally obtain the corn straw paper mulch film. The physical picture of the obtained paper mulch film is as shown in Figure 4 shown. The figure presents the appearance and structural characteristics of the finished product of the straw paper mulch film, showing its uniform surface morphology. The electron micrograph of the obtained paper mulch film is as shown in Figure 5As shown, the microscopic morphology of the plastic film fiber was observed by electron microscopy, showing the cross-linked network structure of the microfibrillated fiber.

[0072] As Figure 6 shown, the figure shows the fiber state after the treatment of the pulp raw material, including the fiber dispersion system with a beating degree of 65-75°SR.

[0073] Mechanical properties: Tested using a universal material testing machine, the dry tensile index is 17 N·m / g, and the wet tensile index is 5.5 N·m / g; the burst resistance index is 3.7 kPa·m 2 / g.

[0074] Water resistance: Tested using a contact angle measuring instrument, the contact angle is 106°, and the water absorption rate in 2 hours is 48%.

[0075] Example 3:

[0076] The green preparation method of the cotton stalk paper mulch film based on thermomechanical pulp is carried out according to the following steps:

[0077] (1) Raw material preparation

[0078] Select dry cotton stalks as raw materials, cut them into small sections with a length of 5 cm, and set aside after cleaning.

[0079] (2) Preliminary hydrothermal treatment

[0080] Put the cotton stalks into a hydrothermal reactor, add water according to a liquid-solid ratio of 10:1, control the temperature at 100 °C, and the treatment time is 1.5 h. The main purpose of this stage is to soften lignin and separate impurities.

[0081] (3) Solid-liquid separation and hydro-abrasion

[0082] Perform solid-liquid separation on the treated cotton stalks to remove the waste liquid. Subsequently, put the cotton stalk fibers into a hydro-abrasion machine and grind them until the fiber length is 1.0 mm. Observe the flexibility and dispersion of the fibers through a microscope to ensure that the fibers reach an ideal state.

[0083] (4) Secondary hydrothermal coupling grinding treatment

[0084] Put the ground fibers back into the hydrothermal reactor, add water according to a liquid-solid ratio of 8:1, control the temperature at 200 °C, perform secondary hydrothermal treatment, and the treatment time is 20 min. After the hydrothermal treatment, start the grinding device until the fiber length is 0.7 mm to further fibrillation the fibers at high temperature.

[0085] (5) Wash-free pulp sizing and sizing

[0086] The processed acidic fiber slurry (pH 4.5) does not require washing. Chitosan (degree of deacetylation ≥ 85%) and epoxy-modified vegetable oil (iodine value 100 g I2 / 100 g) are added to the slurry. The addition amount of chitosan is 3% of the dry weight of the pulp, and the addition amount of epoxy-modified vegetable oil is 2% of the dry weight of the pulp. After stirring evenly, chitosan and acidic pulp form a uniform sizing layer through the electrostatic self-assembly effect.

[0087] (6) Paper mulch film forming and drying

[0088] The sized slurry is formed by a paper machine, and the thickness of the paper mulch film is controlled to be 0.15 mm. The formed paper mulch film is dried at 60 °C for 2 h to remove excess moisture, and finally the cotton stalk paper mulch film is obtained.

[0089] Mechanical properties: Tested using a universal material testing machine, the dry tensile index is 16 N·m / g, and the wet tensile index is 6 N·m / g; the burst resistance index is 4.0 kPa·m 2 / g.

[0090] Water resistance: Tested using a contact angle measuring instrument, the contact angle is 110°, and the water absorption rate in 2 h is 42%.

[0091] Example 4:

[0092] The green preparation method of the ramie stalk paper mulch film based on thermomechanical pulp in this example is carried out according to the following steps:

[0093] (1) Raw material preparation

[0094] Select dry ramie stalks as raw materials, cut them into small sections with a length of 5 cm, wash them clean and set aside.

[0095] (2) Preliminary hydrothermal treatment

[0096] Put the ramie stalks into a hydrothermal reactor, add water according to a liquid-solid ratio of 10:1, control the temperature at 95 °C, and the treatment time is 1.5 h. The main purpose of this stage is to soften lignin and separate impurities.

[0097] (3) Solid-liquid separation and hydrogrinding

[0098] The treated ramie stalks are subjected to solid-liquid separation to remove the waste liquid. Subsequently, the ramie stalk fibers are put into a hydrogrinder and ground until the fiber length is 1.0 mm. Observe the flexibility and dispersibility of the fibers through a microscope to ensure that the fibers reach an ideal state.

[0099] (4) Secondary hydrothermal coupling grinding treatment

[0100] Put the ground fibers back into the hydrothermal reactor, add water at a liquid-solid ratio of 8:1, control the temperature at 200 °C, conduct secondary hydrothermal treatment for 15 min. After the hydrothermal treatment, start the grinding device until the fiber length reaches 0.7 mm to further fibrillationize the fibers at high temperature.

[0101] (5) Sizing and sizing adjustment of the wash-free pulp

[0102] The treated acidic fiber slurry (pH = 4.5) does not need to be washed. Add chitosan (deacetylation degree ≥ 85%) and epoxy-modified vegetable oil (iodine value 100 g I2 / 100 g) to the slurry. The addition amount of chitosan is 3% of the dry weight of the pulp, and the addition amount of epoxy-modified vegetable oil is 2% of the dry weight of the pulp. After stirring evenly, chitosan and acidic pulp form a uniform sizing layer through electrostatic self-assembly effect.

[0103] (6) Molding and drying of the paper mulch

[0104] Form the sized slurry through a paper machine, and control the thickness of the paper mulch to be 0.15 mm. The formed paper mulch is dried at 60 °C for 2 h to remove excess moisture, and finally obtain the ramie stalk paper mulch.

[0105] Mechanical properties: Tested by a universal material testing machine, the dry tensile index is 17 N·m / g, and the wet tensile index is 6 N·m / g; the burst resistance index is 3.9 kPa·m 2 / g.

[0106] Water resistance: Tested by a contact angle measuring instrument, the contact angle is 109°, and the water absorption rate in 2 h is 43%.

[0107] Control example 1: Plastic mulch.

[0108] Manufacturer: Zhejiang Jialemi Horticultural Technology Co., Ltd.

[0109] Model: PBAT biodegradable plastic

[0110] Mechanical properties: Tested by a universal material testing machine, the dry tensile index is 15 N·m / g, and the wet tensile index is 8 N·m / g; the burst resistance index is 4.0 kPa·m 2 / g.

[0111] Water resistance: Tested by a contact angle measuring instrument, the contact angle is 90°, and the water absorption rate in 2 h is 30%.

[0112] Control example 2: Preparation process of ordinary paper mulch:

[0113] Prepare rice straw, dry the rice straw, and then crush the rice straw into long strips with a length of 3 cm. Conduct pulping treatment to obtain pulp. Dissociate the pulp, and then form the dissociated pulp through a paper machine. The formed paper mulch film is dried at 60 °C for 2 h to remove excess moisture, and finally the straw paper mulch film is obtained.

[0114] Mechanical properties: Tested using a universal material testing machine, the dry tensile index is 2 N·m / g, and the wet tensile index is 0.5 N·m / g; the burst resistance index is 2.5 kPa·m 2 / g.

[0115] Water resistance: Tested using a contact angle measuring instrument, the contact angle is 95°, and the water absorption rate in 2 hours is 60%.

[0116] Conclusion:

[0117] The straw paper mulch film of the present invention is significantly superior to the ordinary paper mulch film in terms of mechanical properties. Compared with the traditional plastic mulch film, it has a higher wet tensile strength and can better meet the requirements of wind resistance and soil covering in farmland. The straw paper mulch film of the present invention is significantly superior to the ordinary paper mulch film in terms of water resistance. Compared with the traditional plastic mulch film, it has a higher contact angle and a lower water absorption rate, and can effectively prevent water penetration and maintain soil humidity.

[0118] As mentioned above, it is only the preferred specific implementation manners of the present invention. These specific implementation manners are all different implementation manners based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A green preparation method of straw paper mulch based on thermomechanical pulp, characterized in that: The method: Step 1: placing the straw in a hydrothermal reactor, adding water to submerge the straw, separating the solid and liquid after hydrothermal treatment, and mechanically grinding the obtained solid to a fiber length of 0.8-1.2 mm; Step 2: placing the straw fibers back into the hydrothermal reactor, adding water, and performing a secondary hydrothermal treatment at high temperature, and grinding the fibers again after the hydrothermal treatment until the fiber length is 0.6-0.8 mm to obtain an acidic fiber slurry; Step 3: Use the wash-free pulping technology, add chitosan and epoxy-modified vegetable oil as a composite sizing agent, then form it through a papermaking machine, and obtain the straw paper mulch film after drying.

2. The method according to claim 1, characterized in that The straw in step 1 includes rice straw, corn straw, cotton stalk and hemp stalk.

3. The method according to claim 1, characterized in that In step 1, the hydrothermal treatment temperature is 80-100° C. and the time is 1-2 h.

4. The method according to claim 1, characterized in that: In step 2, the secondary hydrothermal treatment temperature is 180-220° C. and the time is 10-20 min.

5. The method according to claim 1, characterized in that The pH value of the acidic fiber slurry in step 2 is 4-5.

6. The method according to claim 1, characterized in that In step 3, the deacetylation degree of chitosan is ≥85%.

7. The method according to claim 1, characterized in that The iodine value of the epoxy-modified vegetable oil in step 3 is 90-110 gI2 / 100 g.

8. The method according to claim 1, characterized in that: In step 3, the amount of chitosan added is 2-3% of the dry weight of the pulp, and the amount of epoxy-modified vegetable oil added is 1-2% of the dry weight of the pulp.

9. The straw paper mulch film prepared by the method according to any one of claims 1 to 8, characterized in that: The dry tensile index of the straw paper mulch film is ≥15N·m / g, the wet tensile index is ≥5N·m / g, and the bursting index is ≥3.5kPa·m 2 / g, contact angle ≥105°, water absorption rate ≤50% in 2 hours.

10. Use of the straw paper mulch film according to claim 9 in the agricultural field.

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