High-toughness transparent degradable blown film and preparation method thereof

Abstract

The invention discloses a high-toughness transparent degradable blown film and a preparation method thereof, and relates to the field of degradable films. The preparation method of the film comprises the following steps: 1) uniformly mixing the PLA, the PBS, the plasticizer, the epoxy functional group copolymer and the antioxidant in a high-speed mixer in proportion; wherein the components comprise 60-80 parts of PLA, 20-40 parts of PBS, 10-40 parts of a plasticizer, 0.1-1 part of an epoxy functional group copolymer and 1-10 parts of an antioxidant; 2) carrying out melt blending on the mixed material by using a twin-screw extruder, carrying out water-cooling pelletizing on the extruded material, and drying to obtain PLA / PBS composite master batch; and 3) performing blow molding on the PLA / PBS composite master batch by using a single-screw film blowing machine to obtain the high-toughness transparent degradable blown film, the preparation process is simple, and the prepared film has excellent mechanical properties, high transparency and low haze, and is suitable for various packaging applications.

Description

Technical Field

[0001] The invention relates to the field of degradable films, and in particular to a high-toughness transparent degradable blown film and a preparation method thereof. Background Art

[0002] Plastics are widely used in daily life, but traditional petroleum-based plastics, such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), etc., are mainly made from petrochemical materials extracted from coal, oil, and natural gas, and are non-biodegradable. They cannot be completely decomposed in nature, causing serious impacts on the environment.

[0003] Driven by environmental protection needs, biodegradable polymers have gradually come into people's view. Among them, polylactic acid (PLA) is an ideal material for transparent packaging because of its biodegradable properties, good biocompatibility, high tensile strength and high transparency. However, PLA is very brittle and has low melt strength. During the film blowing production process, problems such as bubble rupture and uneven film thickness are prone to occur. The common modification method is to improve the melt strength and film flexibility by blending multiple components with PLA, but it is difficult for the modified film to have both good mechanical properties and high transparency, and cannot meet the application of packaging films with high transparency requirements.

[0004] For example, Chinese patent CN111944287A discloses a method for preparing a highly transparent and tearable polylactic acid blown film. PLA, PBAT and other additives are mixed at high speed, extruded, granulated and dried, and then blown into a film. Although the film has a certain degree of transparency, its mechanical properties are poor and it is difficult to use in packaging.

[0005] Polybutylene succinate (PBS) has high melt strength, thermal stability and flexibility, is very suitable for blown film process, and has higher transparency than PBAT. In the existing technology, PBS and PLA are blended to prepare transparent films. For example, Chinese patent CN113845761A discloses a highly transparent and fully degradable film and its preparation method. Different types of PLA are blended with PBS and other additives, and highly transparent films are prepared by biaxial stretching. However, the mechanical properties of the film prepared by this patent are poor.

[0006] How to prepare a blown film with high transparency, simple preparation process and low cost while ensuring the mechanical properties of the film has become a technical problem that needs to be urgently solved in the current field of biodegradable films. Summary of the invention

[0007] The purpose of the present invention is to solve the above problems in the prior art and provide a high-toughness transparent degradable blown film and a preparation method thereof. The film has excellent optical and mechanical properties and is suitable for various packaging applications.

[0008] In order to achieve the above object, the present invention adopts the following technical scheme:

[0009] A method for preparing a high-toughness transparent degradable blown film comprises the following steps:

[0010] 1) PLA, PBS, plasticizer, epoxy functional copolymer (ADR) and antioxidant are mixed uniformly in a high-speed mixer according to the proportion; wherein PLA 60-80 parts, PBS 20-40 parts, acetyl tributyl citrate 10-40 parts, epoxy functional copolymer 0.1-1 parts, antioxidant 1-10 parts;

[0011] 2) The mixed materials are melt-blended by a twin-screw extruder, and the extrudates are pelletized and dried by water cooling to obtain PLA / PBS composite masterbatch;

[0012] 3) The PLA / PBS composite masterbatch is blown into film by a single-screw film blowing machine to obtain the high-toughness transparent biodegradable blown film.

[0013] The plasticizer is a mixture of one or more of acetyl tributyl citrate (ATBC), tributyl citrate (TBC) and triethyl citrate (TEC).

[0014] The PLA and PBS are PLA and PBS that have been dried.

[0015] In step 2), the feeding speed of the twin-screw extruder is 5-20 rpm, and the main engine speed is 100-500 rpm; the extruder has ten temperature zones from the feed port to the die, and the temperature is set to 140-210°C.

[0016] In step 3), the screw speed of the single screw film blowing machine is 30-60 rpm, the screw heating has five zones, the temperature is set to 160-210° C., the pulling speed is 10-20 rpm, and the winding speed is 10-20 rpm.

[0017] A high-toughness transparent degradable blown film is prepared by the preparation method; the film thickness is 30-100 μm.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0019] (1) The present invention blends PLA and PBS in a certain ratio, modifies the blend by adding acetyl tributyl citrate and epoxy functional group copolymer in different ratios, melt blends and granulates using a twin-screw extruder, and blows the blended masterbatch into a film using a single-screw film blowing machine. The prepared film has excellent mechanical properties and a haze of less than 10%, and maintains high transparency while improving toughness.

[0020] (2) The acetyl tributyl citrate added in the present invention is non-toxic and environmentally friendly, and can effectively improve the elongation at break of the blended film and reduce the haze of the blended film.

[0021] (3) The epoxy functional group copolymer added in the present invention can interact with the hydroxyl and carboxyl groups at the ends of PLA and PBS to improve the compatibility and melt strength of the blend, enable the blend to be blow molded, and improve the mechanical properties of the film.

[0022] (4) The film preparation method of the present invention is blow molding, the performance of the blend meets the blow molding conditions, and the film preparation process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The tensile strength test results of different samples;

[0024] Figure 2 The elongation at break test results of different samples;

[0025] Figure 3 The transmittance test results of different samples are shown in Figure 2.

[0026] Figure 4 The haze test results of different samples. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0028] The present invention will be further described below by means of specific examples.

[0029] The PLA in the examples was purchased from Zhejiang Hisun Biomaterials Co., Ltd., model number Revode 110; PBS was purchased from Xinjiang Blue Mountain Tunhe Polyester Co., Ltd., model number TH803S; acetyl tributyl citrate was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; ADR was purchased from BASF (China) Co., Ltd., model number ADR-4468; and antioxidant was purchased from BASF (China) Co., Ltd., model number 1010.

[0030] Comparative Example 1

[0031] Take 80 parts of PLA and 20 parts of PBS, dry them in an oven at 60℃ for 12 hours, then take 1 part of antioxidant and mix them in a high-speed mixer for 5 minutes. Secondly, melt blend the mixture using a twin-screw extruder. The extruder feeding speed is 10rpm, the main engine speed is 300rpm, and the temperature distribution from the feed section to the die is 140, 190, 190, 190, 190, 195, 195, 200, 200, 200℃. After extrusion, water cool, pelletize and dry to obtain PLA / PBS composite masterbatch. Finally, the composite masterbatch is blown into film using a single-screw film blowing machine. The screw speed of the film blowing machine is 15rpm, the temperatures of the screw heating zones are 180, 180, 190, 190, 180℃, the traction speed is 7rpm, and the winding speed is 8.5rpm to obtain a PLA / PBS composite film. The film thickness is 50μm.

[0032] Example 1

[0033] Take 80 parts of PLA and 20 parts of PBS, dry them in an oven at 60℃ for 12 hours, then take 0.5 parts of ADR-4468, 10 parts of acetyl tributyl citrate, and 1 part of antioxidant, and mix them in a high-speed mixer for 5 minutes. Secondly, melt blend the mixture using a twin-screw extruder, the extruder feeding speed is 10rpm, the main engine speed is 300rpm, and the temperature distribution from the feed section to the die is 140, 190, 190, 190, 190, 195, 195, 200, 200, 200℃, after extrusion, water-cooling, pelletizing and drying to obtain PLA / PBS composite masterbatch. Finally, the composite masterbatch is blown into film using a single-screw film blowing machine, the screw speed of the film blowing machine is 15rpm, the temperatures of the screw heating zones are 180, 180, 190, 190, 180℃, the traction speed is 7rpm, and the winding speed is 8.5rpm to obtain a PLA / PBS composite film. The film thickness is 50 μm.

[0034] Example 2

[0035] Take 80 parts of PLA and 20 parts of PBS, dry them in an oven at 60℃ for 12 hours, then take 0.5 parts of ADR-4468, 15 parts of acetyl tributyl citrate, and 1 part of antioxidant, and mix them in a high-speed mixer for 5 minutes. Secondly, melt blend the mixture using a twin-screw extruder, the extruder feeding speed is 10rpm, the main engine speed is 300rpm, and the temperature distribution from the feed section to the die is 140, 190, 190, 190, 190, 195, 195, 200, 200, 200℃, after extrusion, water-cooling, pelletizing and drying to obtain PLA / PBS composite masterbatch. Finally, the composite masterbatch is blown into film using a single-screw film blowing machine, the screw speed of the film blowing machine is 15rpm, the temperatures of the screw heating zones are 180, 180, 190, 190, 180℃, the traction speed is 7rpm, and the winding speed is 8.5rpm to obtain a PLA / PBS composite film. The film thickness is 50 μm.

[0036] Example 3

[0037] Take 80 parts of PLA and 20 parts of PBS, dry them in an oven at 60℃ for 12 hours, then take 0.5 parts of ADR-4468, 20 parts of acetyl tributyl citrate, and 1 part of antioxidant, and mix them in a high-speed mixer for 5 minutes. Secondly, melt blend the mixture using a twin-screw extruder, the extruder feeding speed is 10rpm, the main engine speed is 300rpm, and the temperature distribution from the feed section to the die is 140, 190, 190, 190, 190, 195, 195, 200, 200, 200℃, after extrusion, water-cooling, pelletizing and drying to obtain PLA / PBS composite masterbatch. Finally, the composite masterbatch is blown into film using a single-screw film blowing machine, the screw speed of the film blowing machine is 15rpm, the temperatures of the screw heating zones are 180, 180, 190, 190, 180℃, the traction speed is 7rpm, and the winding speed is 8.5rpm to obtain a PLA / PBS composite film. The film thickness is 50 μm.

[0038] Example 4

[0039] Take 70 parts of PLA and 30 parts of PBS, dry them in an oven at 60℃ for 12 hours, then take 0.5 parts of ADR-4468, 15 parts of acetyl tributyl citrate, and 1 part of antioxidant, and mix them in a high-speed mixer for 5 minutes. Secondly, melt blend the mixture using a twin-screw extruder, the extruder feeding speed is 10rpm, the main engine speed is 300rpm, and the temperature distribution from the feed section to the die is 140, 190, 190, 190, 190, 195, 195, 200, 200, 200℃, after extrusion, water-cooling, pelletizing and drying to obtain PLA / PBS composite masterbatch. Finally, the composite masterbatch is blown into film using a single-screw film blowing machine, the screw speed of the film blowing machine is 15rpm, the temperatures of the screw heating zones are 180, 180, 190, 190, 180℃, the traction speed is 7rpm, and the winding speed is 8.5rpm to obtain a PLA / PBS composite film. The film thickness is 50 μm.

[0040] Example 5

[0041] Take 60 parts of PLA and 40 parts of PBS, dry them in an oven at 60℃ for 12 hours, then take 0.5 parts of ADR-4468, 15 parts of acetyl tributyl citrate, and 1 part of antioxidant, and mix them in a high-speed mixer for 5 minutes. Secondly, melt blend the mixture using a twin-screw extruder, the extruder feeding speed is 10rpm, the main engine speed is 300rpm, and the temperature distribution from the feed section to the die is 140, 190, 190, 190, 190, 195, 195, 200, 200, 200℃, after extrusion, water-cooling, pelletizing and drying to obtain PLA / PBS composite masterbatch. Finally, the composite masterbatch is blown into film using a single-screw film blowing machine, the screw speed of the film blowing machine is 15rpm, the temperatures of the screw heating zones are 180, 180, 190, 190, 180℃, the traction speed is 7rpm, and the winding speed is 8.5rpm to obtain a PLA / PBS composite film. The film thickness is 50 μm.

[0042] The mechanical properties and optical properties of the PLA / PBS composite films prepared in Comparative Example 1 (D1) and Examples 1 to 5 (S1 to S5) were tested. The specific testing methods are as follows:

[0043] (1) Mechanical properties: Tested according to GB / T1040.3-2006, the samples were cut into 100mm The initial distance between the upper and lower clamps is 50 mm, and the tensile speed is 50 mm / min. The tensile strength and elongation at break are shown in Figure 1 , Figure 2 .

[0044] (2) Optical properties: Tested according to GB / T2410-2008, the samples were cut into 50mm 50mm square piece, measure the transmittance and haze parameters of the composite film, the test results are shown in Figure 3 , Figure 4 .

[0045] As can be seen from the test result diagram, the film prepared by the present invention has good mechanical properties and excellent transparency. According to the test results of Comparative Example 1 and Examples 1 to 3, after adding tributyl acetyl citrate and ADR-4468, whether longitudinally or transversely, the film significantly improves the elongation at break while maintaining tensile strength, and the effect is best when the addition amount of tributyl acetyl citrate is 15 parts, and the elongation at break is increased to 347%. In terms of optical properties, the synergistic effect of tributyl acetyl citrate and ADR-4468 reduces the haze of the modified film from 23% to 7%. Comparative Examples 2, 4 and 5, the proportion of PBS components is increased, so that the haze of the film is improved, and both tensile strength and elongation at break are reduced, and the effect is best when PBS accounts for 20 parts.

Claims

1. A method for preparing a high-toughness transparent degradable blown film, characterized in that: The following steps are involved: 1) PLA, PBS, plasticizer, epoxy functional copolymer and antioxidant are mixed uniformly in a high-speed mixer according to the proportion; wherein PLA 60-80 parts, PBS 20-40 parts, plasticizer 10-40 parts, epoxy functional copolymer 0.1-1 parts, antioxidant 1-10 parts; 2) The mixed materials are melt-blended by a twin-screw extruder, and the extrudates are pelletized and dried by water cooling to obtain PLA / PBS composite masterbatch; 3) The PLA / PBS composite masterbatch is blown into film by a single-screw film blowing machine to obtain the high-toughness transparent biodegradable blown film.

2. The method for preparing a high-toughness transparent degradable blown film according to claim 1, characterized in that: The plasticizer is a mixture of one or more of acetyl tributyl citrate (ATBC), tributyl citrate (TBC) and triethyl citrate (TEC).

3. The method for preparing a high-toughness transparent degradable blown film according to claim 1, characterized in that: The PLA and PBS are PLA and PBS that have been dried.

4. The method for preparing a high-toughness transparent degradable blown film according to claim 1, characterized in that: In step 2), the feeding speed of the twin-screw extruder is 5-20 rpm, and the main engine speed is 100-500 rpm; the extruder has ten temperature zones from the feed port to the die, and the temperature is set to 140-210°C.

5. The method for preparing a high-toughness transparent degradable blown film according to claim 1, characterized in that: In step 3), the screw speed of the single screw film blowing machine is 30-60 rpm, the screw heating has five zones, the temperature is set to 160-210° C., the pulling speed is 10-20 rpm, and the winding speed is 10-20 rpm.

6. A high-toughness transparent biodegradable blown film, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. A high-toughness transparent degradable blown film as claimed in claim 6, characterized in that: The film thickness is 30~100μm.

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