A transparent degradable bubble film and a preparation method thereof

Abstract

The application discloses a kind of transparent degradable bubble film, comprising the following mass ratio of components: cellulose acetate, 50%-80%; plasticizer, 10%-45%; epoxy compound, 0.1-10%.The preparation method of the transparent degradable bubble film includes the following steps: (1) after drying cellulose acetate powder, with plasticizer, epoxy compound is mixed thoroughly;(2) is made into plasticized particle by double-screw extrusion granulation;(3) extruded into film by double-port mold extruder, processed into two films with different thicknesses, thicker film is made into single bubble film by blistering roller, then and another piece of thinner film hot-pressing composite, make bubble film.The elongation at break of the transparent degradable bubble film of the application can reach more than 40%, the light transmittance is high so that the state of the goods in the package can be observed more clearly, while solving the problem that traditional petroleum-based polymer bubble film cannot be degraded in the environment, green and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly materials and relates to transparent, biodegradable packaging materials, especially bubble films that can be used for cushioning and protection, and their preparation methods. Background Technology

[0002] Bubble wrap is a lightweight packaging material generally made from traditional petroleum-based polymers such as polyethylene. It encloses air within the polymer material, providing cushioning and insulation for products, and is widely used in the packaging and transportation industries. In recent years, with the rapid development of new consumption patterns such as online shopping, the usage of bubble wrap has also increased significantly.

[0003] Since polyethylene is difficult to degrade in the atmosphere, the large-scale use of bubble wrap produced from polyethylene will obviously lead to environmental pollution problems.

[0004] To address the aforementioned problem, biodegradable materials such as starch and cellulose can be added to improve the biodegradability of the material. Invention CN108610616A discloses a method for preparing impact-resistant biodegradable bubble film. By filling the expanded porous structure of polyurethane foam with highly resilient polylactic acid and paper fibers, the impact resistance of the bubble film is improved; however, the material cannot be completely decomposed.

[0005] Another approach is to use fully biodegradable materials. CN106566210A relates to a biodegradable bubble film and its preparation method, with polylactic acid and polybutylene adipate terephthalate (PBAT) as the main components. However, films prepared with pure polylactic acid have low elongation at break, generally below 10%, and films modified with flexible materials such as PBAT are opaque. Patent CN111138721A uses heat stabilizers and other additives to improve the stability of cellulose acetate, but in applications requiring high-transparency films, the added inorganic salt heat stabilizers can affect the light transmittance of the final film product. Summary of the Invention

[0006] The purpose of this invention is to provide a transparent biodegradable bubble film and its preparation method. The film has an elongation at break of over 40% and high light transmittance to allow for clearer observation of the contents inside the packaging. At the same time, it solves the problem that bubble films made from traditional petroleum-based polymers cannot degrade in the environment.

[0007] The technical solution adopted by this invention to achieve its objective is as follows:

[0008] A transparent, biodegradable bubble film comprising the following components in the indicated mass ratios:

[0009] Cellulose acetate, 50%-80%;

[0010] Plasticizer, 10%-45%;

[0011] Epoxy compounds, 0.1-10%.

[0012] The above-mentioned transparent and biodegradable bubble film preparation method includes the following steps: 1) After drying cellulose acetate powder, it is thoroughly mixed with plasticizer and epoxy compound; 2) It is granulated by twin-screw extrusion to form plasticized particles; 3) It is extruded into film by a dual-die extruder to form two films with different thicknesses. The thicker film is formed into a single bubble film by blister roller, and then hot-pressed with the other thinner film to form a bubble film.

[0013] The cellulose acetate is obtained by acetylation and hydrolysis of high-purity cellulose acetate, and can be composted. The intrinsic viscosity of cellulose acetate is 1.2-1.8 dL / g, preferably 1.25-1.75 dL / g, more preferably 1.35-1.7 dL / g, and the degree of acetyl substitution ranges from 1.5-2.8, preferably 1.8-2.7, more preferably 1.9-2.6.

[0014] The hydrogen bonding between the hydroxyl groups in the cellulose acetate molecular chains makes it difficult to process directly by heat, and plasticization is required to improve its fluidity and meet the requirements of heat processing and machining.

[0015] Plasticizers can be phthalate esters, commonly including dimethyl phthalate (DMP); diethyl phthalate (DEP); di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), diethyl phthalate (DEP), dioctyl phthalate (DOP), butyl benzyl phthalate (BBP), dioctyl phthalate (DOP), diisononyl phthalate (DINP), diisooctyl phthalate, diisobutyl phthalate, diisooctyl phthalate, diisononyl phthalate, diisodecyl phthalate, dicyclohexyl phthalate, etc.

[0016] Environmentally friendly plasticizers refer to organic compounds or oligomers that do not cause harmful effects on the environment or meet the requirements for food contact materials. A wide range of environmentally friendly plasticizers are available, including one or more combinations of glycerides, citrates, acetylsicitrates, ethylene glycol oligomers, propylene glycol oligomers, ethylene glycol-propylene glycol copolymers, epoxy vegetable oil esters, and other fatty acid ester plasticizers.

[0017] Environmentally friendly plasticizers can also include isosorbide dioctanoate and bio-based polycaprolactone. Isosorbide dioctanoate is synthesized from isosorbide and is a nonionic surfactant used in cosmetics and can also be used as a plasticizer. Bio-based polycaprolactone is a biodegradable material that can be synthesized from hexanediol through hydrogenation of 5-hydroxymethylfurfural via ring-forming and ring-opening polymerization.

[0018] The amount of plasticizer added is 1%-45%, preferably 10%-45%, and more preferably 25%-40%.

[0019] The melt index of cellulose acetate plastic particles prepared with the above plasticizer is 2-20 g / 10 min, and the test conditions are 190℃ and 2.16 kg weight.

[0020] The added epoxy compound can be a flexible chain compound with epoxy groups, such as a polyether compound with a mono-epoxy ring, specifically a polyether compound grafted with epoxy rings treated with epichlorohydrin, such as epoxy polypropylene glycol or epoxy polyfuran glycol. The molecular weight of the epoxy polyether is less than 1000, preferably less than 600. The amount of epoxy compound added needs to be determined experimentally. Although excessive addition can improve the color of the plasticized particles, it will reduce their elongation at break. The amount of epoxy compound added is less than or equal to 10%, preferably less than or equal to 6%, and more preferably less than or equal to 3%.

[0021] The above-mentioned cellulose acetate plasticized particles are melted on an extruder and extruded through a die with two film dies. The extrusion temperature is controlled at 130℃-220℃, preferably 130℃-200℃. The extruded film is stretched, and the thickness of the thicker film is controlled to be 50-300μm, preferably 50-200μm; the thickness of the thinner film is 30-100μm, preferably 30-50μm.

[0022] The thick film, after being extruded and stretched, passes through a vacuum forming roller with concave holes. Before cooling and setting, it is vacuum-formed into a thin film with concave holes of different shapes on its surface. At the same time, the thinner film is stacked on top of it and then hot-pressed to seal the air inside the concave holes, forming a bubble film. The concave holes can be circular, triangular, or trapezoidal, and the depth of the holes can be 1-10 mm.

[0023] This invention utilizes biodegradable cellulose acetate to process biodegradable bubble film. During the plasticizing process, an epoxy compound replaces the role of a heat stabilizer, inhibiting cellulose acetate degradation while avoiding the reduction in light transmittance caused by inorganic salts. The cellulose acetate film plasticized using this method exhibits excellent transparency due to its very low quaternary crystallinity, allowing light to pass through effectively. This facilitates observation of the packaged goods and makes it suitable for cushioning packaging films requiring a certain tensile strength and high transparency. Simultaneously, the epoxy compound contains flexible alkyl groups of a certain chain length. After the epoxy ring reacts with the hydroxyl groups in cellulose acetate, the flexible alkyl segments increase the steric hindrance of the cellulose acetate hydroxyl groups, inhibiting hydrogen bonding between molecular chains and thus plasticizing the cellulose acetate, thereby improving the elongation at break.

[0024] The cellulose acetate bubble film processed by the above process is biodegradable, solving the technical problem that petroleum-based polymer bubble film is difficult to biodegrade, and can be applied in packaging, cushioning and other fields. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] The tensile strength test standard involved in the following cases is GB / T 1040.3-2006, and the transparency test standard is ASTM D1746.

[0027] Example 1

[0028] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of epoxy polypropylene glycol and 300g of triacetin were mixed in a mixer and extruded and granulated at 200℃ using a twin-screw extruder with a melt index of 6g / 10min.

[0029] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 200℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed on a vacuum forming roller into a film with circular concave holes on the surface. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0030] Example 2

[0031] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of epoxy polypropylene glycol and 260g of triacetin were mixed in a mixer and extruded and granulated at 200℃ using a twin-screw extruder with a melt index of 5g / 10min.

[0032] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 200℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed on a vacuum forming roller into a film with circular concave holes on the surface. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0033] Example 3

[0034] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of epoxy polypropylene glycol and 376g of triethyl acetyl citrate were mixed in a mixer and extruded and granulated at 200℃ using a twin-screw extruder with a melt index of 8g / 10min.

[0035] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 200℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed on a vacuum forming roller into a film with circular concave holes on the surface. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0036] Example 4

[0037] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of epoxy polypropylene glycol, 150g of triacetin, and 150g of triethyl citrate were mixed in a mixer and extruded and granulated at 210℃ using a twin-screw extruder with a melt index of 5g / 10min.

[0038] 2. The plasticized particles are extruded into shape using a single-screw extruder at a die temperature of 210℃. Simultaneously, a thick film with a thickness of 120μm and a thin film with a thickness of 50μm are extruded. The thick film is processed on a thermoforming roller into a film with circular concave holes on the surface, with a hole diameter of 5mm and a depth of 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0039] Example 5

[0040] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, it is mixed with 150g of triacetin and 150g of acetylic acid triester in a mixer, and then extruded and granulated using a twin-screw extruder at 215℃ with a melt index of 4g / 10min.

[0041] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 215℃. At the same time, a thick film with a thickness of 150μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0042] Example 6

[0043] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of epoxy polypropylene glycol and 300g of ethyl phthalate were mixed in a mixer and extruded and granulated using a twin-screw extruder at 205℃ with a melt index of 6g / 10min.

[0044] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0045] Example 7

[0046] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of epoxy polypropylene glycol and 376g of ethyl phthalate were mixed in a mixer and extruded and granulated using a twin-screw extruder at 205℃ with a melt index of 8g / 10min.

[0047] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0048] Example 8

[0049] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 3.5g of epoxy polypropylene glycol and 376g of ethyl phthalate were mixed in a mixer and extruded and granulated at 205℃ using a twin-screw extruder with a melt index of 8g / 10min.

[0050] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0051] Example 9

[0052] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 14g of epoxy polypropylene glycol and 376g of ethyl phthalate were mixed in a mixer and extruded and granulated at 205℃ using a twin-screw extruder with a melt index of 7g / 10min.

[0053] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0054] Example 10

[0055] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 3.5g of epoxy polypropylene glycol and 233g of ethyl phthalate were mixed in a mixer and extruded and granulated at 205℃ using a twin-screw extruder with a melt index of 5g / 10min.

[0056] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0057] Example 11

[0058] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of polyethylene glycol (molecular weight 400) with epoxy groups and 300g of PEG600 were mixed in a mixer and extruded and granulated using a twin-screw extruder at 210℃ with a melt index of 5g / 10min.

[0059] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 150μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0060] Example 12

[0061] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 0.7g of epoxy polypropylene glycol and 233g of ethyl phthalate were mixed in a mixer and extruded and granulated at 205℃ using a twin-screw extruder with a melt index of 5g / 10min.

[0062] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 100μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0063] Example 13

[0064] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 7g of polyethylene glycol (molecular weight 400) with epoxy groups and 170g of PEG600 were mixed in a mixer and extruded and granulated using a twin-screw extruder at 210℃ with a melt index of 1.6g / 10min.

[0065] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. The resulting film is uneven and the tensile properties are reduced.

[0066] Comparative Example 1

[0067] 1. After drying 700g of cellulose acetate powder at 120℃ for 2 hours, 10103g of antioxidant and 300g of triacetin were mixed in a mixer and extruded and granulated using a twin-screw extruder at 210℃ with a melt index of 5g / 10min.

[0068] 2. The plasticized particles are extruded into shape using a single-screw extruder with a die temperature of 205℃. At the same time, a thick film with a thickness of 150μm and a thin film with a thickness of 50μm are extruded. The thick film is processed into a film with circular concave holes on the surface on a thermoforming roller. The diameter of the concave holes is 5mm and the depth is 6mm. The thick film and the thin film are then hot-pressed to form a bubble film.

[0069] Table 1. Analysis of Test Results

[0070] Thin film types Tensile strength (MPa) Elongation at break (%) transparency(%) Example 1 38 61 91 Example 2 43 52 89 Example 3 36 63 93 Example 4 45 60 90 Example 5 41 61 90 Example 6 43 55 91 Example 7 42 63 93 Example 8 38 67 92 Example 9 46 53 95 Example 10 46 44 89 Example 11 7 27 90 Example 12 46 44 86 Comparative Example 1 39 42 85 PBAT membrane 22 573 70

[0071] Note: For ease of comparison, the film thickness is 50 μm.

[0072] As shown in the table above, the film formed by plasticizing cellulose acetate according to the present invention, compared with Comparative Example 1, shows that the elongation at break of plasticized cellulose acetate with added epoxy compounds is increased by at least 24%, and the transparency is increased to at least 90%. It can achieve an elongation at break of over 50%, a tensile strength of over 38 MPa, and maintain a transparency of over 90%, which can meet the requirements for preparing transparent bubble films with certain tensile strength. In contrast, if PEG is used, the tensile strength and elongation at break are relatively low, as shown in Example 10.

[0073] The foregoing descriptions and embodiments are provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be easily made to these contents, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the foregoing descriptions and embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from its scope should be within the protection scope of the present invention.

Claims

1. A transparent, biodegradable bubble film, characterized in that, It consists of the following components in the indicated mass ratio: Cellulose acetate, 50%-80%; Plasticizer, 10%-45%; Epoxy compounds, 0.1%-10%; The epoxy compound is epoxy polypropylene glycol with a molecular weight of less than 1000 and containing a single epoxy group; the elongation at break of the bubble film is more than 40%. The method for preparing the transparent biodegradable bubble film includes the following steps: (1) drying cellulose acetate powder and then mixing it thoroughly with plasticizer and epoxy compound; (2) granulating it by twin-screw extrusion to form plasticized particles; (3) extruding it into a film by a dual-die extruder to process it into two films of different thicknesses. The thicker film is made into a single bubble film by a blister roller and then hot-pressed with the other thinner film to form a bubble film. In step (3), the plasticized particles are melted on an extruder and extruded through a die with two film dies. The extruded film is stretched, and the thickness of the thicker film is controlled to be 50-300µm; the thickness of the thinner film is controlled to be 30-100µm; and the extrusion temperature is controlled to be 130℃-220℃.

2. The transparent biodegradable bubble film according to claim 1, characterized in that: The intrinsic viscosity of the cellulose acetate is 1.2-1.8 dL / g.

3. The transparent biodegradable bubble film according to claim 1, characterized in that: The intrinsic viscosity of the cellulose acetate is 1.25-1.75 dL / g.

4. The transparent biodegradable bubble film according to claim 1, characterized in that: The intrinsic viscosity of the cellulose acetate is 1.35-1.7 dL / g.

5. The transparent biodegradable bubble film according to claim 1, characterized in that: The degree of acetyl substitution of the cellulose acetate ranges from 1.5 to 2.

8.

6. The transparent biodegradable bubble film according to claim 1, characterized in that: The degree of acetyl substitution of the cellulose acetate ranges from 1.8 to 2.

7.

7. The transparent biodegradable bubble film according to claim 1, characterized in that: The degree of acetyl substitution of the cellulose acetate ranges from 1.9 to 2.

6.

8. The transparent biodegradable bubble film according to claim 1, characterized in that: The content of the plasticizer is 25%-40%.

9. The transparent biodegradable bubble film according to claim 1, characterized in that: The plasticizers include dimethyl phthalate; diethyl phthalate; dibutyl phthalate, dioctyl phthalate, butyl benzyl phthalate, diisobutyl phthalate, diisooctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and dicyclohexyl phthalate.

10. The transparent biodegradable bubble film according to claim 1, characterized in that: The plasticizer includes one or more combinations of glycerides, citrates, and acetylic acid esters.

11. The transparent biodegradable bubble film according to claim 1, characterized in that: The plasticizer includes one or more combinations of epoxy vegetable oil esters and other fatty acid ester plasticizers.

12. The transparent biodegradable bubble film according to claim 1, characterized in that: The plasticizer is isosorbide dioctanoate.

13. The transparent biodegradable bubble film according to claim 1, characterized in that: The amount of the epoxy compound added is less than or equal to 6% and greater than or equal to 0.1%.

14. The transparent biodegradable bubble film according to claim 1, characterized in that: The amount of the epoxy compound added is less than or equal to 3% and greater than or equal to 0.1%.

15. A method for preparing the transparent biodegradable bubble film according to claim 1, characterized in that, The process includes the following steps: (1) Drying cellulose acetate powder and then mixing it thoroughly with plasticizer and epoxy compound; (2) Granulating it by twin-screw extrusion to form plasticized particles; (3) Extruding it into a film by a dual-die extruder to form two films of different thicknesses. The thicker film is made into a single bubble film by a blister roller and then hot-pressed with the other thinner film to form a bubble film.

16. The method for preparing the transparent biodegradable bubble film according to claim 15, characterized in that: Step (3): The cellulose acetate plasticized particles are melted on an extruder and extruded through a die with two film dies. The extruded film is stretched to control the thickness of the thicker film to be 50-200µm and the thickness of the thinner film to be 30-50µm.

17. The method for preparing the transparent biodegradable bubble film according to claim 16, characterized in that: The extrusion temperature is controlled between 130℃ and 200℃.

18. The method for preparing the transparent biodegradable bubble film according to claim 15, characterized in that: Step (3): The thick film that has been extruded and stretched passes through a vacuum forming roller with concave holes. Before cooling and shaping, it is vacuum-formed into a thin film with concave holes on the surface by negative pressure adsorption. At the same time, the thinner film is stacked on top of it and then hot-pressed to seal the air in the concave holes to form a bubble film.

19. The method for preparing the transparent biodegradable bubble film according to claim 18, characterized in that: The concave hole is circular, triangular, or trapezoidal in shape.

20. The method for preparing the transparent biodegradable bubble film according to claim 18, characterized in that: The depth of the recessed hole is 1-10mm.