Low-cost high-performance biodegradable PBAT-PLA composite film and preparation method thereof

Abstract

The invention discloses a low-cost high-performance biodegradable PBAT-PLA composite film. The composite film is prepared from the following raw materials: 79-81.5% of PBAT-PLA master batch; 18-20% of a functional component; 0.5 to 1% of CaO; the sum of the mass percentages of all the components is 100%. Wherein the PBAT-PLA master batch is prepared from PBAT and PLA according to the mass ratio of (15 to 19): 1; the functional component is one of bamboo powder, lignin and straw powder. According to the invention, PBAT-PLA master batch is obtained by controlling PBAT and PLA in a certain mass ratio, then 18-20wt% of low-cost functional component (one of bamboo powder, straw powder and lignin) is compounded, and especially the functional component lignin is added, so that the biodegradable PBAT-PLA composite film with low cost, good thermal stability and thermal processability and high mechanical property is obtained. The garbage bag prepared from the composite film has good leakage resistance.

Description

Technical Field

[0002] The present invention relates to the technical field of film materials and preparation thereof, and in particular to a low-cost, high-performance, biodegradable PBAT-PLA composite film and a preparation method thereof. Background Art

[0003] Plastic film products such as garbage bags have become an indispensable part of daily life. They are mainly made of non-degradable polyolefins. Due to the serious phenomenon of random discarding of plastics during use, plastic waste is now spread throughout many ecosystems on the earth, including deep sea trenches, remote mountainous areas, air, and even polar regions. It is well known that polyolefins degrade slowly in nature, causing "white pollution" problems and huge economic losses. Therefore, the development and use of green and degradable materials is the mainstream trend of the times.

[0004] PBAT is a thermoplastic biodegradable polymer material with excellent biodegradability, ductility and heat resistance. It is one of the most active biodegradable materials in the research of biodegradable plastics and the best biodegradable materials in the market. However, the disadvantages of PBAT resin such as easy adhesion during processing limit its application in the field of film materials. For this reason, PBAT is often compounded with other environmentally friendly materials. Studies have found that PLA has the characteristics of strong rigidity. Melting and blending PLA and PBAT can help improve the strength of the composite material. At present, commercial PBAT-PLA products have been launched on the market, but the product price is relatively high, and there are still disadvantages such as poor thermal stability, strong viscosity and poor processing performance, as well as insufficient toughness, which limits the large-scale production and application of this type of material. Therefore, improving the performance of the film while effectively reducing the cost of PBAT-PLA film is an important measure to promote its industrial production. Summary of the invention

[0005] The present invention aims to at least partially overcome the above-mentioned technical problems and / or other potential problems existing in the prior art: to provide a biodegradable PBAT-PLA composite film with low cost, good thermal stability and thermal processing performance, and high mechanical properties, and a preparation method thereof, and the garbage bag prepared from the composite film has good leakage resistance.

[0006] The first object of the present invention is to provide a low-cost, high-performance biodegradable PBAT-PLA composite film, the raw materials for its preparation include the following components: PBAT-PLA masterbatch 79-81.5%; functional component 18-20%; CaO 0.5-1%; the sum of the mass percentages of all the above components is 100%; wherein the PBAT-PLA masterbatch is composed of PBAT and PLA in a mass ratio of (15-19):1; the functional component is one of bamboo powder, lignin, and straw powder.

[0007] Preferably, the bamboo powder has a fineness of 400-800 mesh; the lignin has a fineness of 1800-2000 mesh; and the straw powder has a fineness of 400-800 mesh.

[0008] The second object of the present invention is to provide a method for preparing a high-performance biodegradable PBAT-PLA composite film, comprising the following steps: 1) Dry the raw materials PBAT resin, PLA resin, functional components and CaO at 80-85°C for 12-24h; 2) First, add the dried PBAT resin and PLA resin into a mixer at a mass ratio of (15-19):1 and mix for 5-10 minutes; then add the mixture into a twin-screw extruder for melt blending and extrusion, and obtain PBAT-PLA masterbatch after water cooling, air drying and pelletizing; 3) The PBAT-PLA masterbatch prepared in step 2) is mixed with the functional component and CaO in the following ratio: PBAT-PLA masterbatch 79-81.5%; functional component 18-20%; CaO 0.5-1%; the obtained composite material is added into a twin-screw extruder for melt blending and extrusion, and the functionalized composite masterbatch is obtained by water cooling, air drying and pelletizing; 4) Dry the functionalized composite masterbatch prepared in step 3) at 80-85° C. for 12-24 hours, then add it to a film blowing machine for melt extrusion film blowing, and control the film thickness to 10-12 μm to obtain a high-performance biodegradable PBAT-PLA composite film.

[0009] Preferably, the feed rate of the extruder in step 2) and step 3) is 150 g / min, and the extrusion temperature zones are set to five temperature zones of 175 / 170 / 165 / 165 / 160°C.

[0010] Preferably, in step 4), the five temperature zones of the film blowing machine are set to 165 / 165 / 160 / 155 / 150°C, and the screw speed is 60 r / min.

[0011] The beneficial effect of the present invention is as follows: the present invention obtains PBAT-PLA masterbatch by controlling a certain mass ratio of PBAT and PLA, and then compounds 18-20wt% of a low-cost functional component (one of bamboo powder, straw powder and lignin), especially the addition of the functional component lignin, to obtain a biodegradable PBAT-PLA composite film with low cost, good thermal stability and thermal processing performance, and high mechanical properties, and the garbage bag prepared from the composite film has good leakage resistance.

[0012] The present invention can promote the industrial production and application of PBAT-PLA products, promote the widespread application of biodegradable resins, meet the national green, degradable, and sustainable development strategic requirements, and have important application prospects. The raw material resources of the functional components of the present invention are abundant and low in cost, which helps to reduce the cost of PBAT-PLA products. Based on the current market price of raw materials, the raw material cost per ton of composite film is further calculated. The results show that the raw material cost of the film of the present invention is reduced by 17.73% at most compared with the existing PBAT-PLA products. The addition of functional components can reduce the use of expensive biodegradable resins, save costs, and facilitate promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a morphology picture of the garbage bag prepared in Example 1.

[0014] Figure 2 This is a SEM microscopic morphology comparison of the garbage bags PPL and PP prepared in Example 1 and Comparative Example 1.

[0015] Figure 3 TG, DTG and DSC curves of the garbage bags PPL and PP prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below with specific examples, but the present invention is not limited to the following specific examples.

[0017] Material preparation Raw materials: PBAT resin, 8003f, Hangzhou Xinfu Technology Co., Ltd.; PLA resin, 4032D, Nature Works, USA; Bamboo powder, 38 μm, passed through 400 mesh sieve, Longmen County Shenglong Bamboo and Wood Co., Ltd.; Lignin, 8 μm, 1800 mesh sieve, Jining Mingsheng New Materials Co., Ltd.; Straw powder, 38μm, 400 mesh sieve, Shaanxi Jinhe Agricultural Science and Technology Co., Ltd. Main equipment and instruments: Co-rotating parallel twin-screw extruder, KTE-20, Nanjing Kerke Extrusion Equipment Co., Ltd.; Plastic bag extrusion blow molding machine, JS-200, Ruian Tongchuang Plastic Packaging Machinery Co., Ltd. Example 1 1) Dry the raw materials PBAT resin, PLA resin, lignin and CaO at 80°C for 12h; 2) First, the dried PBAT resin and PLA resin were added to a high-speed mixer at a mass ratio of 15:1 and mixed for 5 minutes; then the mixture was added to a twin-screw extruder for melt blending and extrusion, and the PBAT-PLA masterbatch was obtained after water cooling, air drying and pelletizing; wherein the feed rate was 150 g / min, and the extrusion temperature zone was set to 175 / 170 / 165 / 165 / 160 ℃.

[0018] 3) The PBAT-PLA masterbatch prepared in step 2) is mixed with lignin and CaO in the following ratio: PBAT-PLA masterbatch 79.2%; lignin 19.80%; CaO 1%; the obtained composite material is added into a twin-screw extruder for melt blending and extrusion, and the functionalized composite masterbatch is obtained by water cooling, air drying and pelletizing; wherein the feed rate is 150 g / min, and the extrusion temperature zone is set to 175 / 170 / 165 / 165 / 160 ℃.

[0019] 4) The functionalized composite masterbatch prepared in step 3) was dried at 80°C for 12h, and then added into a plastic bag film blowing machine. The temperature zones were set to 165 / 165 / 160 / 155 / 150°C, and the screw speed was 60 r / min. Melt extrusion film blowing and bag making were performed. The thickness of the composite garbage bag film was controlled to be about 10 μm, and the length and width were 37 cm×30 cm. In this embodiment, the extrusion traction direction was the longitudinal direction of the film, and the film blowing expansion direction was the transverse direction of the film. The composite garbage bag sample prepared in this embodiment is referred to as PPL, and its macroscopic morphology is as follows: Figure 1 shown.

[0020] Performance Testing Leakage resistance test: According to GB / T24454-2009, about 10L of tap water was added to the PPL garbage bag prepared in this embodiment. Figure 1 As shown, when the water level reaches 2 / 3, pinch the mouth of the garbage bag and hang it, and observe whether there is water leakage within 5 minutes. The number of samples is 5; the results show that there is no water leakage in the garbage bags, the quality is good, and the heat sealing performance is excellent. The PPL garbage bag is soft, light, and dark brown, which shows that lignin has good dispersion properties and promotes the mechanical properties of PPL.

[0021] Example 2 The difference from Example 1 is that the lignin in the raw material is replaced by bamboo powder, and the prepared composite garbage bag is referred to as PPB.

[0022] Example 3 The difference from Example 1 is that the lignin in the raw material is replaced by straw powder, and the prepared composite garbage bag is referred to as PPS.

[0023] Example 4 The difference from Example 1 is that in step 2), the mass ratio of PBAT resin to PLA resin is 19:1; in step 3), PBAT-PLA masterbatch is mixed with functional components and CaO according to the following ratio: PBAT-PLA masterbatch 79%; lignin 20%; CaO 1%.

[0024] Example 5 The difference from Example 1 is that in step 2), the mass ratio of PBAT resin to PLA resin is 16:1; in step 3), PBAT-PLA masterbatch is mixed with functional components and CaO according to the following ratio: PBAT-PLA masterbatch 81%; lignin 18%; CaO 1%.

[0025] Comparative Example 1 1) Dry the raw materials PBAT resin, PLA resin and CaO at 80°C for 12h; 2) First, the dried PBAT resin and PLA resin were added into a high-speed mixer at a mass ratio of 15:1 and mixed for 5 minutes; then the mixture was added into a twin-screw extruder for melt blending and extrusion, and the PBAT-PLA masterbatch was obtained after water cooling, air drying and pelletizing; wherein the feed rate was 150 g / min, and the extrusion temperature zone was set to 175 / 170 / 165 / 165 / 160 ℃.

[0026] 3) The PBAT-PLA masterbatch prepared in step 2) is mixed with CaO in the following ratio: PBAT-PLA masterbatch 99%; CaO 1%; the obtained composite material is added to a twin-screw extruder for melt blending and extrusion, and the composite masterbatch is obtained by water cooling, air drying and pelletizing; wherein the feed rate is 150 g / min, and the extrusion temperature zone is set to 175 / 170 / 165 / 165 / 160 °C.

[0027] 4) The composite masterbatch prepared in step 3) was dried at 80°C for 12 h, and then added into a plastic bag film blowing machine. The temperature zones were set to 165 / 165 / 160 / 155 / 150°C and the screw speed was 60 r / min. Melt extrusion film blowing and bag making were performed. The film thickness of the composite garbage bag was controlled at about 10 μm, and the length and width were 37 cm×30 cm. In this embodiment, the extrusion traction direction was the longitudinal direction of the film, and the film blowing expansion direction was the transverse direction of the film. The prepared composite garbage bag is referred to as PP.

[0028] Data analysis Good dispersion of the functional components in the film matrix is ​​a necessary condition for the composite film to have good performance. In order to observe the dispersion of the PLA / PBAT / lignin composite garbage bag prepared in Example 1 in the film matrix, the surface morphology of the PPL prepared in Example 1 and the PP film prepared in Comparative Example 1 was observed by SEM, as shown in FIG. Figure 2As shown. By observing the microscopic morphology of the sample film, it can be seen that lignin has good dispersion in the PBAT / PLA matrix, and the surface of PPL is the smoothest. There are obvious holes on the fracture surface of the PP film. This is because the PLA used to enhance the performance of the film is incompatible with PBAT. PLA particles fall off during the quenching process. However, after the addition of lignin, the holes on the fracture surface of the film are significantly reduced. The addition of lignin increases the compatibility of PBAT and PLA.

[0029] The TG and DTG curves of PP and PPL are shown in Figure 3 (a). The thermal decomposition of the composite film starts after 250 °C, and the corresponding mass loss temperatures of 10% are 373.50 and 363.34 °C, respectively. PPL has good thermal stability. This is because the addition of lignin will limit the heat conduction and the overflow rate of cracked small molecules, which is conducive to the formation of a carbon layer during the pyrolysis process and improves the thermal stability of the composite film. It can be seen from the DTG curve that the maximum mass loss temperatures of PP and PPL are 413.89 and 415.12, respectively. PPL has good heat resistance. This is because the addition of lignin can increase the maximum mass loss rate of the composite film and improve its stability. PP, PPL DSC curves are shown in Figure 3 (b). The results show that the melting temperatures of the two composite films are almost the same, with the melting endothermic peak of PBAT at around 120 °C and the melting peak temperature of PLA at around 160 °C, indicating that the functional components have no significant effect on their melting temperatures. By calculation, the crystallinity of PBAT in PP and PPL composite films is 12.28% and 14.60%, respectively, of which PBAT has the highest crystallinity in PPL; the crystallinity of PLA in PP and PPL composite film bags is 35.19% and 13.02%, respectively, of which the crystallinity of PLA is significantly reduced after the addition of lignin, which is mainly because the addition of lignin has a plasticizing effect on PLA and improves the compatibility of the polymer.

[0030] Based on the current market price of raw materials, the raw material costs of PLA / PBAT composite film and PLA / PBAT / lignin per ton were further calculated, which were 22,537 and 18,540 yuan respectively. The results showed that the cost of PLA / PBAT / lignin (PPL for short) was reduced by 17.73% compared with PP film. The addition of lignin filler can reduce the use of expensive biodegradable resin, save costs, and facilitate promotion and application.

[0031] The above are only examples of the features of the present invention and do not constitute any limitation on the protection scope of the present invention. Any technical solution formed by equivalent exchange or equivalent replacement falls within the protection scope of the present invention.

Claims

1. A low-cost, high-performance, biodegradable PBAT-PLA composite film, characterized in that: The raw materials for its preparation include the following components: PBAT-PLA masterbatch 79-81.5%; functional component 18-20%; CaO 0.5-1%; the sum of the mass percentages of all the above components is 100%; wherein the PBAT-PLA masterbatch is composed of PBAT and PLA in a mass ratio of (15-19):1; the functional component is one of bamboo powder, lignin, and straw powder.

2. The low-cost, high-performance biodegradable PBAT-PLA composite film according to claim 1, characterized in that: The bamboo powder has a fineness of 400-800 meshes; the lignin has a fineness of 1800-2000 meshes; and the straw powder has a fineness of 400-800 meshes.

3. A method for preparing the low-cost, high-performance, biodegradable PBAT-PLA composite film according to claim 1 or 2, characterized in that: The following steps are involved: 1) Dry the raw materials PBAT resin, PLA resin, functional components and CaO at 80-85°C for 12-24h; 2) First, add the dried PBAT resin and PLA resin into a mixer at a mass ratio of (15-19):1 and mix for 5-10 minutes; then add the mixture into a twin-screw extruder for melt blending and extrusion, and obtain PBAT-PLA masterbatch after water cooling, air drying and pelletizing; 3) The PBAT-PLA masterbatch prepared in step 2) is mixed with the functional component and CaO in the following ratio: PBAT-PLA masterbatch 79-81.5%; functional component 18-20%; CaO 0.5-1%; the obtained composite material is added into a twin-screw extruder for melt blending and extrusion, and the functionalized composite masterbatch is obtained by water cooling, air drying and pelletizing; 4) Dry the functionalized composite masterbatch prepared in step 3) at 80-85° C. for 12-24 hours, then add it to a film blowing machine for melt extrusion film blowing, and control the film thickness to 10-12 μm to obtain a low-cost, high-performance, biodegradable PBAT-PLA composite film.

4. The method for preparing a low-cost, high-performance, biodegradable PBAT-PLA composite film according to claim 3, characterized in that: The feed rate of the extruder in step 2) and step 3) was 150 g / min, and the extrusion temperature zones were set at 175 / 170 / 165 / 165 / 160 °C.

5. The method for preparing a low-cost, high-performance, biodegradable PBAT-PLA composite film according to claim 3, characterized in that: Step 4) The temperature zones of the film blowing machine were set to 165 / 165 / 160 / 155 / 150 °C and the screw speed was 60 r / min.

Images