Biodegradable mulching film for garlic and new garlic planting mode

Abstract

The invention provides a biodegradable mulching film for garlic and a new garlic planting mode. The biodegradable mulching film for garlic is prepared from the following components in parts by weight: 65 to 87 parts of PBAT; 12 to 35 parts of calcium carbonate; 0.2 to 1 part of a lubricant; 0.2 to 1 part of a light stabilizer; 0.1 to 1 part of a crosslinking hydrolysis stabilizer; and 0.2 to 0.5 part of an antioxidant. Calcium carbonate is creatively introduced, and the adding proportion is optimized, so that the puncture resistance of the biodegradable mulching film is lower than 1.2 N, meanwhile, the longitudinal breaking force of the biodegradable mulching film is larger than 2N, the garlic self-breaking film emergence rate is larger than 90%, and the requirement for mechanical laying can be met. And the puncture resistance is further reduced by adjusting the particle size of calcium carbonate and adding a crosslinking hydrolysis stabilizer with proper functionality. The biodegradable mulching film has the advantages of low puncture resistance, high longitudinal breaking force, long service life and the like, and the use of the biodegradable mulching film and the acre yield of garlic are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of biodegradable mulch films, and relates to a biodegradable mulch film for garlic and a new garlic planting mode. Background Art

[0002] The planting time of garlic is generally in the late autumn season. After a whole winter of dormancy differentiation and gradual accumulation of nutrients, the garlic bulbs can rapidly expand after turning green in spring, ensuring the quality and yield of garlic. Garlic is a crop that is cold-resistant but afraid of freezing, and likes humidity but is afraid of waterlogging. The vast North China Plain is suitable for growing garlic, but extreme low temperatures may occur. When the temperature is lower than -10°C, garlic freeze damage will occur. At the same time, excessive drought will lead to a decline in garlic quality. Therefore, it is necessary to cover the ground with a mulch film to keep the temperature and moisture for the growth of garlic.

[0003] The yield per mu of garlic after covering with a mulch film can generally be increased by 20% compared with that without covering. Since the garlic needs to break through the mulch film after germination to continue growing, currently, polyethylene mulch films with a thickness of less than 6 microns are widely used for large-scale garlic planting. If the thickness is too high, the garlic seedlings cannot break through the mulch film, and neither manual seedling picking nor mechanical film breaking can achieve good results. However, the mandatory national standard for polyethylene stipulates that the thickness of polyethylene mulch films must not be less than 10 microns, which naturally results in that polyethylene mulch films meeting the national standards cannot be used for garlic planting.

[0004] There is no limit to the use thickness of biodegradable mulch films, and ultra-thin and functionalized biodegradable mulch films can be achieved after meeting the use performance. Since the mechanical properties of the biodegradable mulch films gradually decline, and the puncture resistance of the initial film is even higher than that of polyethylene mulch films, the existing 8-micron biodegradable mulch films cannot achieve good automatic film-breaking and seedling-emergence effects during the garlic germination and film-breaking stage about one week after the mulch film is laid, and a large amount of labor is required for mechanical or manual film breaking.

[0005] The purpose of the present invention is to solve the problem of automatic film-breaking and seedling-emergence of garlic after laying the biodegradable mulch film, and at the same time ensure that the biodegradable mulch film has good mechanical strength and a certain service life to ensure stable production of garlic. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a biodegradable mulch film for garlic and a new garlic planting mode. The puncture resistance of the biodegradable mulch film of the present invention is less than 1.2 N, and most of the garlic can break through the film and emerge by itself, and the self-breaking and seedling-emergence rate of garlic is greater than 90%; at the same time, the longitudinal breaking force of the biodegradable mulch film is greater than 2 N, meeting the requirements of mechanical laying; in addition, the service life is not less than 180 days. The biodegradable mulch film of the present invention has the advantages of low puncture resistance, high longitudinal breaking force and long service life, ensuring the use of the biodegradable mulch film and the yield per mu of garlic.

[0007] In the years of garlic planting and experience in regulating the performance of supporting degradable mulch films, it has been found that it is very difficult for garlic to break through the mulch film by its own strength during the emergence stage. Even when using degradable mulch films with a thickness of 6 microns or less, a good self-breaking and emergence rate cannot be achieved. Through repeated comparison of the performance of mulch films and research combined with the growth of garlic, it has been found that the puncture resistance of the degradable mulch film is an important factor affecting the emergence and film breaking of garlic. Once the puncture resistance of the degradable mulch film is greater than 1.2 N, the self-breaking and emergence rate of garlic is less than 70%. Subsequently, a large amount of manual or mechanical secondary film breaking or even more times of film breaking is required, which not only generates more costs, but also the excessive external force during the film breaking stage will significantly affect the service life of the biodegradable mulch film, and is not conducive to the long-term protection of the degradable mulch film during the growth stage of garlic; once the puncture resistance of the degradable mulch film is less than 1.2 N, the self-breaking and emergence rate of garlic will exceed 90%, greatly reducing the operation of manual or mechanical film breaking; further, when the puncture resistance is less than 0.8 N, the self-breaking and emergence rate of garlic reaches 95%, and basically no secondary film breaking is required, avoiding the damage of external force to the mulch film and ensuring the long-term protection of the biodegradable mulch film for the growth of garlic.

[0008] At the same time, to ensure that the biodegradable mulch film meets the requirements of machine laying, the longitudinal breaking force needs to be greater than 2 N. Otherwise, the degradable mulch film is prone to break during the laying process. Further, the longitudinal breaking force needs to be greater than 2.5 N to meet the mechanical laying in various environments. It should be noted that it is difficult to achieve maintaining a high breaking force while ensuring a low puncture resistance of the film. The two mechanical properties will basically increase or decrease simultaneously.

[0009] The present invention unexpectedly discovers that by adjusting the appropriate calcium carbonate particle size and ratio, and simultaneously cooperating with the above cross-linked hydrolysis stabilizer, the unique performance of low puncture resistance and high longitudinal breaking force can be simultaneously satisfied. With the use of a light stabilizer, a service life of more than 180 days can be guaranteed.

[0010] First of all, calcium carbonate reduces the breaking force of the mulch film. However, with the addition of calcium carbonate, the elongation at break of the mulch film shows a trend of first increasing and then decreasing, and the puncture resistance of the mulch film gradually decreases with the increase of the calcium carbonate addition amount. Therefore, a range needs to be considered. Within this range, the large-scale production efficiency and production stability are guaranteed, and at the same time, the breaking force and elongation at break meet the requirements of mechanical laying and actual use, while the puncture resistance reaches the level where garlic can automatically break through the film and emerge. It is further found that after meeting the requirements of the addition ratio, the particle size of calcium carbonate will also affect the actual puncture resistance. Calcium carbonate with a particle size between 1000 mesh and 3000 mesh preferably meets the requirements.

[0011] Secondly, to meet the requirement that the degradable mulch film has a certain longitudinal breaking force, a certain proportion of crosslinked hydrolysis stabilizer is added in the present invention. It has reactive groups with polymer materials, which can, to a certain extent, increase the molecular weight of the matrix material and the entanglement degree between chains, improve the breaking force and tearing force, and maintain certain properties when weakening the breaking force by calcium carbonate. And the present invention finds that the crosslinked hydrolysis stabilizer with low functionality can increase the longitudinal breaking force while minimally increasing the puncture resistance.

[0012] Finally, considering the cost of the degradable mulch film and its performance matching, the thickness is an important consideration factor. Considering the relationship between cost and performance comprehensively, the thickness of the degradable mulch film for garlic is controlled between 4 - 8 microns. Within this thickness range, the production and use of a better functionalized degradable mulch film can be realized.

[0013] In summary, within this thickness range, by adjusting the appropriate size and addition amount of calcium carbonate, and cooperating with a certain proportion of hydrolysis stabilizer to control the chain entanglement degree, the purpose of the present invention can be achieved.

[0014] The purpose of the present invention is achieved through the following solutions:

[0015] In the first aspect, the present invention provides a biodegradable mulch film for garlic, comprising the following components in parts by weight:

[0016] PBAT: 65 - 87 parts;

[0017] Calcium carbonate: 12 - 35 parts;

[0018] Lubricant: 0.2 - 1 part;

[0019] Light stabilizer: 0.2 - 1 part;

[0020] Crosslinked hydrolysis stabilizer: 0.1 - 1 part;

[0021] Antioxidant: 0.2 - 0.5 part.

[0022] In the present invention, when the addition amount of calcium carbonate is between 12 - 35 parts, the requirement that the puncture resistance is less than 1.2 N and the longitudinal breaking force is greater than 2 N can be met, and the degradable mulch film meets the requirements for garlic growth during actual use. When the addition amount of calcium carbonate is greater than 35 parts, although a low puncture resistance can be ensured, too much calcium carbonate destroys the continuity between polymer chains, the breaking force of the degradable mulch film drops rapidly, and the processability is damaged to a certain extent, and it can no longer meet the requirements of machine laying. When the calcium carbonate content is less than 12 parts, the puncture resistance of the mulch film is too high, and the automatic film-breaking and seedling-emergence rate is less than 70%.

[0023] As an embodiment of the present invention, the weight portion of the calcium carbonate is 18 - 30 parts. When the addition amount of calcium carbonate is between 18 - 30 parts, while meeting the requirement of garlic breaking through the film and emerging, the processability of the degradable film is more stable, and it can meet the large-scale production and stable use in the field at the same time.

[0024] As an embodiment of the present invention, the particle size of the calcium carbonate is 1000 - 3000 mesh. When the particle size of calcium carbonate is greater than 3000 mesh, the overly fine calcium carbonate not only fails to reduce the puncture resistance, but instead has an overall enhancing effect on the mechanical properties of the degradable film. If too much calcium carbonate is added to achieve a lower puncture resistance, it will significantly increase the material cost and on the other hand, it will affect the aging performance of the degradable film and cannot achieve a service life of 180 days. If the mesh number of calcium carbonate is too small, there will be problems with its dispersion in the film, and the diameter is too large to smoothly prepare a thin degradable film. The average diameter of the calcium carbonate in the present invention is 4 - 13 microns.

[0025] As an embodiment of the present invention, the crosslinking hydrolysis stabilizer includes one or several of polyfunctional epoxy compounds (more than bifunctional, less than hepta-functional), polyfunctional low-polymerization degree carbodiimides (more than bifunctional, less than hepta-functional), and polyfunctional isocyanates (more than bifunctional, less than hepta-functional); wherein, the polyfunctionality is between 3 and 6. The crosslinking hydrolysis stabilizer with appropriate functionality can increase the molecular weight without causing excessive crosslinking between molecular chains and affecting the puncture resistance of the degradable film.

[0026] In some embodiments, the crosslinking hydrolysis stabilizer includes any one of epoxy compounds (KL120), polymeric carbodiimides (HyMax210), and hexamethylene diisocyanate-based polyisocyanates (HT600).

[0027] As an embodiment of the present invention, the thickness of the biodegradable film for garlic is 4 - 8 microns. Reducing the thickness can directly reduce the puncture resistance of the degradable film, but if it is not functionally treated, its basic tensile fracture and other properties will also decrease accordingly, thus affecting the actual laying and the maintenance of the service life. Although increasing the thickness can meet the mechanical properties and can also achieve automatic film breaking and emergence of garlic by reducing the puncture resistance, due to the increase in thickness and the need to add functional components, the cost will increase directly. Once the thickness is lower than 4 microns, although the aging resistance life and performance can meet the requirements of garlic planting, the molecular chain structure of the polymer chain body has begun to be damaged, and a uniform degradable film cannot be achieved at the microstructural level, and defects have occurred in the overall film, which will have some impact on the growth of garlic. If the thickness is higher than 8 microns, although stable production and application can be achieved by adjusting the added components and ratios, the direct cost affects the market promotion.

[0028] As an embodiment of the present invention, the lubricant includes one or more of amide lubricants, stearic acid and stearate lubricants, low-molecular-weight olefin lubricants, silicone oil lubricants, and silica. The light stabilizer includes one or more of UV531, UV1164, UV-P, UV944, UV234, and silica white. The antioxidant includes one or more of BHT, 1024, DSTP, 168, 1076, and 1010.

[0029] In a second aspect, the present invention provides a method for preparing the biodegradable mulching film for garlic, comprising the following steps:

[0030] S1. Mix PBAT with a crosslinking hydrolysis stabilizer;

[0031] S2. Add calcium carbonate, a lubricant, a light stabilizer, and an antioxidant to the mixture in step S1, stir, and then perform extrusion granulation and blow molding to obtain the product.

[0032] As an embodiment of the present invention, in step S1, the mixing is carried out using a high-speed mixer, the mixing time is 3 - 5 minutes, and the mixing temperature is 82 - 85°C. Through high-speed stirring, weak crosslinking is generated between the crosslinking hydrolysis stabilizer and PBAT. On the one hand, it can make the crosslinking hydrolysis stabilizer more evenly distributed in the system. On the other hand, due to the generation of preliminary weak crosslinking, the undistributed and evenly dispersed uncrosslinked parts will not cause excessive crosslinking in the product finally. The use of a crosslinking hydrolysis stabilizer with a certain functionality in combination with the processing method can achieve better results.

[0033] As an embodiment of the present invention, in step S2, the stirring time is 2 - 4 minutes, and the temperature is 20 - 40°C. Stirring can prevent the functional additives from failing during the mixing process.

[0034] As an embodiment of the present invention, in step S2, the extrusion granulation is carried out using a twin-screw extruder, and the temperature of the extruder for extrusion granulation is 120 - 180°C. After extrusion granulation, blow molding is carried out in a single-screw blown film machine to obtain the biodegradable mulching film with the final required thickness.

[0035] In a third aspect, the present invention provides an application of the biodegradable mulching film in garlic planting.

[0036] In a fourth aspect, the present invention provides a new garlic planting mode. In the new garlic planting mode, except for less than 10% that cannot break through the film and emerge by itself and needs to be manually broken through the film and dug out the seedlings, there is no need for large-scale mechanical film breaking or manual film breaking and seedling digging in other cases; and the service life is not less than 180 days. The service life refers to the time from laying to the time when there are 5 gaps not greater than 2 cm per 1 meter not less than 180 days.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. By adjusting the proportion of specific calcium carbonate and cooperating with the cross-linking hydrolysis stabilizer, the puncture resistance of the biodegradable plastic film is less than 1.2 N, and most of the garlic can break through the film and emerge by itself, with the emergence rate of garlic breaking through the film by itself being greater than 90%, greatly reducing the operation of manual or mechanical film breaking; at the same time, the longitudinal breaking force of the biodegradable plastic film is greater than 2 N, which can meet the mechanical laying in various environments.

[0039] 2. Further, by adjusting the particle size of specific calcium carbonate, on the one hand, the requirement of puncture resistance is preferably met; on the other hand, it is beneficial to improve the aging performance of the biodegradable plastic film and extend its service life.

[0040] 3. By adding a light stabilizer, the present invention further extends the service life of the biodegradable plastic film, making its service life not less than 180 days, meeting the requirements of long-term use.

[0041] 4. The product preparation method involved in the present invention is simple and easy to implement, and can be rapidly promoted; at the same time, the specific processing method involved in the present invention can accurately prepare the degradable plastic film with the required functions of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects and advantages of the present invention will become more apparent:

[0043] Figure 1 It shows the film-breaking situation when garlic has just emerged;

[0044] Figure 2 It shows the complete situation of garlic emergence. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The present invention will be described in detail below with reference to the drawings and specific embodiments. The following examples are implemented on the premise of the technical solution of the present invention, providing detailed implementation manners and specific operation processes, which will help those skilled in the art to further understand the present invention. It should be noted that the protection scope of the present invention is not limited to the following embodiments, and several adjustments and improvements made under the premise of the concept of the present invention all belong to the protection scope of the present invention.

[0046] The materials used in Examples 1-11 and Comparative Examples 1-10 are as follows:

[0047] A) PBAT resin: Tongcheng New Materials Group Co., Ltd., RA-WR290;

[0048] B-1) Calcium carbonate: Zhejiang Jiande Zhengfa Calcium Carbonate Co., Ltd., mesh number 8000 mesh;

[0049] B-2) Calcium carbonate: Jiangxi Guangyuan Chemical Co., Ltd., mesh number 3000;

[0050] B-3) Calcium carbonate: Jiangsu Dongli Superfine Powder Co., Ltd., mesh number 800;

[0051] B-4) Calcium carbonate: Jiangsu Dongli Superfine Powder Co., Ltd., mesh number 1250;

[0052] B-5) Calcium carbonate: Jiangsu Dongli Superfine Powder Co., Ltd., mesh number 2000;

[0053] B-6) Calcium carbonate: Jiangsu Dongli Superfine Powder Co., Ltd., mesh number 3000;

[0054] B-7) Calcium carbonate: Jiangsu Dongli Superfine Powder Co., Ltd., mesh number 4000;

[0055] C) Lubricant: Jining Huipeng Chemical Co., Ltd., oleic acid amide;

[0056] D) Light stabilizer: Tianjin Lian An Long New Materials Co., Ltd., UV531;

[0057] E-1) Crosslinking hydrolysis stabilizer: Shanghai Langyi Functional Materials Co., Ltd., KL120, six functional groups;

[0058] E-2) Crosslinking hydrolysis stabilizer: Shanghai Langyi Functional Materials Co., Ltd., HyMax 210, four functional groups;

[0059] E-3) Crosslinking hydrolysis stabilizer: Wanhua Chemical Group Co., Ltd., HT600, three functional groups;

[0060] F-1) Antioxidant: Beijing Jiyi Holdings Group Co., Ltd., 168;

[0061] F-2) Antioxidant: Beijing Jiyi Holdings Group Co., Ltd., 1010;

[0062] The components of Examples 1-10 and Comparative Examples 1-10 are shown in Tables 1 and 2.

[0063] The product processing steps involved in the examples and comparative examples are as follows:

[0064] S1. Mix PBAT with the corresponding crosslinking hydrolysis stabilizer at a high speed for 4 minutes according to the proportions shown in Tables 1 and 2, and control the temperature during high-speed mixing at 85°C;

[0065] S2. Add a certain proportion of calcium carbonate, lubricant, light stabilizer, and antioxidant to the mixture after the end of Step S1, and stir at a high speed for 3 minutes, controlling the stirring temperature at 40°C.

[0066] S3. Add the materials mixed in step S2 into a twin-screw extruder, and control the temperature of the extruder between 120°C and 180°C to extrude and pelletize.

[0067] S4. Blow the obtained pellets in a single-screw blown film machine to obtain a degradable ground film with the final required thickness.

[0068] Table 1

[0069]

[0070]

[0071] Table 2

[0072]

[0073] Use the ground film with a thickness of 4 μm prepared in Example 2 for garlic planting, and its film-breaking situation is as Figure 1-2 shown; among them, Figure 1 is when the seedlings just start to emerge, and it can be clearly seen that the garlic seedlings break through the degradable ground film; Figure 2 is Figure 1 15 days after emergence, all the garlic seedlings break through the film and emerge on their own.

[0074] The test data of Examples 1-10 are shown in Tables 3 and 4.

[0075] The test method for the longitudinal breaking force mentioned in the present invention is tested according to GB / T 1040.3, type 2 specimen.

[0076] The test method for the puncture resistance is tested according to GB / T 37841-2019, and the puncture speed is 50 mm / min.

[0077] Table 3

[0078]

[0079] Table 4

[0080]

[0081] The test data of Comparative Examples 1-10 are shown in Table 5.

[0082] Table 5

[0083]

[0084] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A biodegradable plastic film, characterized in that, Comprising the following components in parts by weight: PBAT: 65 - 87 parts; Calcium carbonate: 12 - 35 parts; Lubricant: 0.2 - 1 part; Light stabilizer: 0.2 - 1 part; Crosslinking hydrolysis stabilizer: 0.1 - 1 part; Antioxidant: 0.2 - 0.5 part.

2. The biodegradable ground film according to claim 1, wherein, The weight parts of the calcium carbonate are 18 - 30 parts.

3. The biodegradable ground film according to claim 1, wherein, The particle size of the calcium carbonate is 1000 - 3000 mesh.

4. The biodegradable ground film according to claim 1, wherein The crosslinking hydrolysis stabilizer includes one or several of polyfunctional low - polymerization - degree carbodiimide, polyfunctional isocyanate, and polyfunctional epoxy compound; wherein, the polyfunctionality is between 3 and 6.

5. The biodegradable ground film according to claim 4, wherein, The crosslinking hydrolysis stabilizer includes any one of polymeric carbodiimide HyMax210, hexamethylene diisocyanate - based polyisocyanate HT600, and epoxy compound KL120.

6. The biodegradable ground film according to claim 1, wherein The lubricant includes one or several of amide lubricants, stearic acid and stearate lubricants, low - molecular - weight olefin lubricants, silicone oil lubricants, and silica; And / or, the light stabilizer includes one or several of UV531, UV1164, UV - P, UV944, UV234, and silica white; And / or, the antioxidant includes one or several of BHT, 1024, DSTP, 168, 1076, and 1010.

7. The biodegradable ground film according to claim 1, wherein The thickness of the biodegradable mulch film for garlic is 4 - 8 microns.

8. A method for preparing the biodegradable mulching film according to any one of claims 1-7, characterized in that, Comprising the following steps: S1. Mix PBAT with the crosslinking hydrolysis stabilizer; S2. Add calcium carbonate, lubricant, light stabilizer, and antioxidant to the mixture in step S1, stir, and then carry out extrusion granulation and blow molding to obtain.

9. The preparation method according to claim 8, characterized in that, In step S1, the mixing is carried out by a high - speed mixer, the mixing time is 3 - 5 minutes, and the mixing temperature is 82 - 85 °C.

10. Use of the biodegradable mulch film according to any one of claims 1 - 7 in garlic planting.

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