Method for producing a multilayer film based on ultrafine straw / calcium carbonate powder and product thereof

Abstract

The present invention discloses a method for manufacturing a multilayer film based on ultrafine straw / calcium carbonate powder, including: (1) mixing coarse straw powder and ultrafine calcium carbonate, pulverizing, and sieving to obtain ultrafine straw / calcium carbonate powder with a mesh size of 500-2000; (2) mixing PBAT, PLA, compatibilizer, epoxidized soybean oil, silane coupling agent, and the ultrafine straw / calcium carbonate powder, and manufacturing them into composite particles through a twin-screw extrusion granulator; (3) inflating the composite particles through an inflation molding machine to manufacture a multilayer film. In the method described in the present invention, the 1000-mesh yield of the straw powder is 30% or more. The addition of calcium carbonate powder can significantly improve the straw pulverization effect, effectively avoid electrostatic adsorption or aggregation between calcium carbonate powders and between straw powders, and the calcium carbonate powder does not need to be separated from the straw powder and can function as a multilayer film opening agent. The present invention further discloses a multilayer film manufactured by the above method, which has relatively good tensile strength and elongation at break.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a multifilm, and particularly to a method for manufacturing a multifilm based on ultrafine straw / calcium carbonate powder and its products, belonging to the field of agricultural applications.

Background Art

[0002] Against the background that China strongly advocates the "dual carbon" strategy, the application of degradable materials is becoming increasingly widespread, such as degradable multifilms, garbage bags, etc. However, currently, the problems faced by degradable materials are mainly that the raw material prices are high and the performance is lower than that of conventional materials such as PE, so it is difficult to use them on a large scale. Since degradable multifilms also face the same problems, there is an urgent need for improvement measures that can not only reduce the cost of degradable materials but also improve their performance to a certain extent. In the prior art, Chinese Invention Patent CN104403174A discloses a method for filling a PBAT multifilm with calcium carbonate. The addition of calcium carbonate reduces the cost of the material. However, since too much calcium carbonate is added to the multifilm, calcium carbonate is lost in the soil during the decomposition process of the multifilm, hardening the land, which is disadvantageous for subsequent cultivation. Therefore, it has no practicality.

[0003] Crop straw is one of the most abundant biomass materials in nature. When applied to a multifilm, it not only improves the utilization of agricultural waste but also can be dispersed into the soil as the multifilm decomposes, realizing the effect of reusing the straw in agricultural land. In the prior art, Chinese Invention Patent CN113461983A discloses a method of filling a PBAT film with modified straw powder. First, the straw is crushed to 500 - 800 meshes, then the powder is modified, and finally added to the PBAT film. The elongation at break of the produced PBAT film is 430 - 460%, and the tensile strength is 32.24 - 36.43 MPa. The addition of straw powder can reduce costs, but the costs of straw crushing and modification cannot be ignored. In addition, during the straw crushing process, the energy consumption due to low crushing efficiency increases the cost. On the other hand, because the straw particles are large, it is impossible to manufacture a thin agricultural multifilm at all, increasing the cost and significantly degrading the multifilm performance. Therefore, there are also certain limitations in the actual application of this technology.

[0004] From the above, it is desirable to provide a method for manufacturing a simple and efficient straw / PBAT composite multifilm. Therefore, the production and modification of large-mesh straw powder are also particularly important. Simple wheat straw is soft in nature during the crushing process, making it difficult to achieve a good crushing effect. The yield of pure straw powder crushed for 3 hours passing through a 1000-mesh sieve (10 μm) is only 3 - 9%.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a multifilm based on ultrafine straw / calcium carbonate powder that effectively increases the tensile strength and a method for manufacturing the same.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides the following technical solutions.

[0007] The present invention provides a method for manufacturing a multifilm based on ultrafine straw / calcium carbonate powder, (1) mixing coarse straw powder and ultrafine calcium carbonate, pulverizing, and sieving to obtain ultrafine straw / calcium carbonate powder of 500-2000 mesh; (2) mixing PBAT, PLA, compatibilizer, epoxidized soybean oil, silane coupling agent and the ultrafine straw / calcium carbonate powder, and manufacturing as composite particles through a twin-screw extrusion granulator; (3) inflating the composite particles through an inflation molding machine to manufacture a multifilm.

[0008] In step (1), the mesh number of the coarse powder is 50-100 mesh, which is beneficial for continuous grinding after mixing the calcium carbonate powder.

[0009] In step (1), the mass ratio of the coarse powder to the ultrafine calcium carbonate is 1-4:1, and the mesh number of the ultrafine calcium carbonate powder is 1000-2000 mesh, which can greatly improve the pulverization effect and avoid electrostatic adsorption or aggregation between calcium carbonate powders and between straw powders.

[0010] In step (1), the pulverization time is 2-3 h, which ensures sufficient pulverization of the ultrafine straw / calcium carbonate powder.

[0011] In step (2), the mass ratio of PBAT, PLA, compatibilizer, epoxidized soybean oil, silane coupling agent and ultrafine straw / calcium carbonate powder is 200-800:10-180:2-20:1-15:1-20:20-300.

[0012] The compatibilizer includes an acid anhydride type compatibilizer, an epoxy type compatibilizer or an ethylene terpolymer.

[0013] In step 2), the extrusion temperature of the twin-screw extrusion granulator is 180 - 200 °C in the first zone, 170 - 190 °C in the second zone, 170 - 190 °C in the third zone, 160 - 180 °C in the fourth zone, and 150 - 170 °C in the fifth zone, and the rotational speed of the main body is 40 - 80 rpm.

[0014] In step 3), the inflation temperature of the inflation molding machine is 180 - 200 °C in the first zone, 170 - 190 °C in the second zone, 170 - 190 °C in the third zone, 165 - 185 °C in the fourth zone, 160 - 180 °C in the fifth zone, and 150 - 170 °C in the sixth zone.

[0015] In step (3), the rotational speed of the main body of the inflation molding machine is 10 - 30 rpm, and the traction speed is 5 - 25 rpm.

[0016] The present invention further provides a multifilm produced by the above method.

[0017] Reaction mechanism: Since the ultrafine calcium carbonate powder itself has a small particle size and a hard material, it can function as a grinding abrasive similar to small balls in a ball mill, and the ultrafine calcium carbonate powder is sufficiently dispersed in the straw powder, so that electrostatic adsorption or aggregation between the calcium carbonate powders and between the straw powders can be avoided.

Advantages of the Invention

[0018] Compared with the prior art, the present invention has the following three remarkable advantages.

[0019] 1. After mixing the ultrafine calcium carbonate powder and the straw powder, a good grinding effect can be achieved, and the yield of 1000-mesh straw powder is more than 30%. 2. There is no need to separate the ultrafine calcium carbonate powder from the straw powder, and it can be added to the multifilm simultaneously as an anti-blocking agent. 3. The produced ultrafine straw / calcium carbonate powder can enhance the tensile strength of the multifilm.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying out the Invention

[0021] Hereinafter, the technical solution of the present invention will be further described with reference to the drawings.

[0022] Materials: Wheat straw is derived from the Jiangsu Academy of Agricultural Sciences; ultrafine calcium carbonate powder (1000 - 2000 mesh): Suzhou Shengyao Plastic New Materials Co., Ltd., lot number SY - 2700; thermoplastic biodegradable plastic (PBAT): Jinhui Zhaolong High - tech Co., Ltd., lot number 1908; silane coupling agent (PLA): Cargill, lot number 2003D; compatibilizer: ethylene terpolymer, DuPont, USA, HP441; silane coupling agent: Sinopharm Chemical Reagent Co., Ltd., KH570; epoxidized soybean oil: Microlink.

[0023] Equipment: Twin - screw extrusion granulator: Zhangjiagang Lianjiang Machinery Co., Ltd., LJPS20 - PLC; inflation molding machine: Zhangjiagang Lianjiang Machinery Co., Ltd., SCM25 - PLC.

[0024] Example 1 When ultrafine calcium carbonate powders with particle sizes of 1000 mesh, 1500 mesh, and 2000 mesh were respectively selected and sieved, it was found that the amounts of the 1000 - mesh, 1500 - mesh, and 2000 - mesh ultrafine calcium carbonate powders after sieving were small, and certain aggregation occurred among the calcium carbonate powders, resulting in an increase in particle size.

[0025] Production of ultrafine straw / calcium carbonate powder: Wheat straw was ground and sieved to obtain a coarse powder of wheat straw of about 50 mesh. Next, the coarse powder of wheat straw and the ultrafine calcium carbonate powder of 1000 mesh sieved were mixed at a mass ratio of 4:1. Then, it was put into a pulverizer and pulverized for 3 hours to obtain a mixture, which was sieved through a 1000-mesh sieve to obtain the ultrafine straw / calcium carbonate powder.

[0026] Production of multilayer film: 200 parts of PBAT, 10 parts of PLA, 2 parts of compatibilizer, 1 part of epoxidized soybean oil (chemical formula: (RC2H2OR’COO)3C3H5), 1 part of silane coupling agent, and 20 parts of ultrafine straw / calcium carbonate powder were uniformly mixed in a ratio and manufactured as composite particles through a twin-screw extrusion granulator. The twin-screw extrusion temperature was 190 °C in the first zone, 180 °C in the second zone, 180 °C in the third zone, 170 °C in the fourth zone, and 160 °C in the fifth zone, and the rotational speed of the main body was 60 rpm. Next, when inflated by an inflation molding machine, a multilayer film with a thickness of 10 μm was manufactured. The inflation temperature was 190 °C in the first zone, 180 °C in the second zone, 180 °C in the third zone, 175 °C in the fourth zone, 170 °C in the fifth zone, and 160 °C in the sixth zone, the rotational speed of the main body was 20 rpm, and the traction speed was 15 rpm.

[0027] Example 2 Production of ultrafine straw / calcium carbonate powder: Wheat straw was ground and sieved to obtain a coarse powder of wheat straw of about 80 mesh. Next, the coarse powder of wheat straw and the ultrafine calcium carbonate powder of 2000 mesh were mixed at a mass ratio of 2:1. Then, it was put into a pulverizer and pulverized for 2 hours to obtain a mixture, which was sieved through a 1000-mesh sieve to obtain the ultrafine straw / calcium carbonate powder.

[0028] Manufacture of Multifilm: 800 parts of PBAT, 180 parts of PLA, 20 parts of compatibilizer, 15 parts of epoxidized soybean oil, 20 parts of silane coupling agent, and 300 parts of ultrafine straw / calcium carbonate powder were uniformly mixed in a ratio and manufactured into composite particles through a twin-screw extrusion granulator. The twin-screw extrusion temperature was 200 °C in the first zone, 190 °C in the second zone, 190 °C in the third zone, 180 °C in the fourth zone, and 170 °C in the fifth zone, and the rotational speed of the main body was 80 rpm. Next, when inflated by an inflation molding machine, a multifilm with a thickness of 10 μm was manufactured. The inflation temperature was 200 °C in the first zone, 190 °C in the second zone, 190 °C in the third zone, 185 °C in the fourth zone, 180 °C in the fifth zone, and 170 °C in the sixth zone, the rotational speed of the main body was 30 rpm, and the drawing speed was 25 rpm.

[0029] Example 3 Manufacture of Ultrafine Straw / Calcium Carbonate Powder: Wheat straw was polished and sieved to obtain coarse powder of wheat straw of about 100 mesh. Next, the coarse powder of wheat straw and ultrafine calcium carbonate powder of 1500 mesh were mixed at a mass ratio of 1:1, then put into a pulverizer and pulverized for 2.5 hours to obtain a mixture, which was sieved through a 1000-mesh sieve to obtain ultrafine straw / calcium carbonate powder.

[0030] Manufacture of Multifilm: 500 parts of PBAT, 100 parts of PLA, 10 parts of compatibilizer, 10 parts of epoxidized soybean oil, 10 parts of silane coupling agent, and 200 parts of ultrafine straw / calcium carbonate powder were uniformly mixed in a ratio and manufactured into composite particles through a twin-screw extrusion granulator. The twin-screw extrusion temperature was 180 °C in the first zone, 170 °C in the second zone, 170 °C in the third zone, 160 °C in the fourth zone, and 150 °C in the fifth zone, and the rotational speed of the main body was 40 rpm. Next, when inflated by an inflation molding machine, a multifilm with a thickness of 10 μm was manufactured. The inflation temperature was 180 °C in the first zone, 170 °C in the second zone, 170 °C in the third zone, 165 °C in the fourth zone, 160 °C in the fifth zone, and 150 °C in the sixth zone, the rotational speed of the main body was 10 rpm, and the drawing speed was 5 rpm.

[0031] Example 4 Manufacture of ultrafine straw / calcium carbonate powder: Wheat straw was ground, screened to obtain a coarse powder of wheat straw of about 50 mesh, and then the coarse powder of wheat straw and calcium carbonate powder of about 500 mesh were mixed at a mass ratio of 1:1. Next, it was put into a pulverizer and pulverized for 3 hours to obtain a mixture, which was then sieved through a 500-mesh sieve to obtain ultrafine straw / calcium carbonate powder.

[0032] Manufacture of multilayer film: 600 parts of PBAT, 150 parts of PLA, 18 parts of compatibilizer, 12 parts of epoxidized soybean oil, 18 parts of silane coupling agent, and 250 parts of ultrafine straw / calcium carbonate powder were uniformly mixed in a ratio and manufactured as composite particles through a twin-screw extrusion granulator. The parameters of the twin-screw extruder and the inflation molding machine are the same as those in Example 1.

[0033] Example 5 Examination of the grinding efficiency of ultrafine straw / calcium carbonate powder at various ratios Taking pure wheat straw as a comparative example, it was put into a pulverizer and pulverized for 3 hours. As shown in Figure 1, the yields of 1000 mesh and above in Examples 1 to 4 were 35.9%, 51.8%, 30.2%, and 15.7% respectively, all of which were higher than the yield of 5.1% of pure wheat straw. Thus, with the increase in the ratio of calcium carbonate, the yield of 1000 mesh and above also increases. However, if the calcium carbonate content is too high, it will cause a decrease in the grinding efficiency. That is, when the mass ratio of the coarse powder of wheat straw to ultrafine calcium carbonate powder is 2:1, it was found that the yield of 1000 mesh and above is the highest.

[0034] Example 6 Examination of the influence of the content of ultrafine straw / calcium carbonate powder by sieving Using pure wheat straw powder and ultrafine calcium carbonate as comparative examples, the infrared spectra of the straw / calcium carbonate powder before and after sieving in Example 2 were measured. As shown in Figure 2, the hydroxyl peak of the straw / calcium carbonate powder in Example 2 after sieving through a 1000-mesh sieve was almost the same as that without sieving. This indicates that it is not due to an increase in the calcium carbonate content and a decrease in the straw content, but rather that the ratio of straw to calcium carbonate hardly changes, and sieving has little adverse effect on the contents of calcium carbonate and straw.

[0035] Example 7 Examination of the particle size of ultrafine straw powder Using pure straw powder as a comparative example, scanning electron microscopy was performed on the straw / calcium carbonate powder in Example 2. As shown in Figure 3, the average particle size of the straw powder in the straw / calcium carbonate powder is 6 μm, which is significantly smaller than 30 μm of simple straw grinding, indicating that the addition of calcium carbonate can significantly improve the grinding efficiency.

[0036] Example 8 Examination of the mechanical properties of various multilayer films Using the multilayer film produced by the method of Example 1 with pure straw powder as a comparative example. Mechanical property tests were performed on the multilayer films of Examples 1 to 4. As shown in Figure 4, the tensile strength of the multilayer film added with pure straw powder is 14.87 MPa, and the elongation at break is 488.01%. The tensile strengths of the multilayer films produced in Examples 1 to 4 are 21.83 MPa, 26.23 MPa, 21.00 MPa, and 22.9 MPa respectively, and the elongations at break are 450.60%, 528.10%, 397.15%, and 447.6% respectively. In the multilayer film added with pure straw powder, spots were clearly visible, causing a decrease in its mechanical properties and also indicating the occurrence of aggregation. In contrast, in the present invention, by adding straw / calcium carbonate powder to PBAT, not only can the tensile strength be significantly improved, but the elongation at break also improves to a certain extent, showing a very positive effect in modifying the multilayer film.

Claims

1. (1)A step of mixing coarse straw powder and ultrafine calcium carbonate powder, pulverizing them, and sieving to obtain ultrafine straw / calcium carbonate powder of 500 to 2000 mesh; (2)A step of mixing PBAT, PLA, a compatibilizer, epoxidized soybean oil, a silane coupling agent, and the ultrafine straw / calcium carbonate powder, and manufacturing them as composite particles through a twin-screw extrusion granulator; (3)A method for manufacturing a multifilm based on ultrafine straw / calcium carbonate powder, comprising a step of inflating the composite particles through an inflation molding machine to manufacture a multifilm.

2. In the step (1), the coarse straw powder is 50 to 100 mesh, and the method according to Claim 1 is characterized by this.

3. In the step (1), the mass ratio of the coarse straw powder to the ultrafine calcium carbonate is 1 to 4:1, and the ultrafine calcium carbonate powder is 1000 to 2000 mesh, and the method according to Claim 1 is characterized by this.

4. In the step (1), the pulverizing time is 2 to 3 h, and the method according to Claim 1 is characterized by this.

5. In the step (2), the mass ratio of the PBAT, PLA, compatibilizer, epoxidized soybean oil, silane coupling agent, and ultrafine straw / calcium carbonate powder is 200 to 800:10 to 180:2 to 20:1 to 15:1 to 20:20 to 300, and the method according to Claim 1 is characterized by this.

6. The compatibilizer includes an acid anhydride type compatibilizer, an epoxy type compatibilizer, or an ethylene terpolymer, and the method according to Claim 5 is characterized by this.

7. In the step (2), the extrusion temperature of the twin-screw extrusion granulator is 180 to 200 °C in the first zone, 170 to 190 °C in the second zone, 170 to 190 °C in the third zone, 160 to 180 °C in the fourth zone, and 150 to 170 °C in the fifth zone, and the rotation speed of the main body is 40 to 80 rpm, and the method according to Claim 1 is characterized by this.

8. In the step (3), the inflation temperature of the inflation molding machine is 180 to 200 ° C in the first zone, 170 to 190 ° C in the second zone, 170 to 190 ° C in the third zone, 165 to 185 ° C in the fourth zone, 160 to 180 ° C in the fifth zone, and 150 to 170 ° C in the sixth zone. The method according to claim 1, characterized in that.

9. In the step (3), the rotation speed of the main body of the inflation molding machine is 10 to 30 rpm, and the traction speed is 5 to 25 rpm. The method according to claim 5, characterized in that.

10. A multi-film produced by the method according to any one of claims 1 to 9.

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