NL2034760A

NL2034760A - Weather-resistant biodegradable film, and preparation method and use thereof

Info

Publication number: NL2034760A
Application number: NL2034760A
Authority: NL
Inventors: Liu Qi; He Wenqing
Original assignee: Inst Of Environment And Sustainable Development In Agriculture Chinese Academy Of Agricultural Scien
Priority date: 2022-05-07
Filing date: 2023-05-04
Publication date: 2023-11-14
Also published as: CN114573960B; CN114573960A

Abstract

The present disclosure provides a weather-resistant biodegradable film, and a preparation method and use thereof, and belongs to the technical ﬁeld of degradable materials. In the present disclosure, a foamer, a cross-linking agent, and a photoinitiator are added to raw materials. During processing, the foamer is decomposed by heat to generate tiny air bubbles, which wrap a part of the cross- linking agent. The wrapped cross-linking agent does not react with a biodegradable polyester during the processing, and is uniformly dispersed in a processed ﬁlm. During use, the tiny air bubbles burst, releasing the cross-linking agent under protection. Through an action of the photoinitiator, the cross-linking agent gradually undergoes cross-linking with the polyester, and can effectively slow down breakage of polyester molecular chains or partially re-ligate broken molecules.

Description

WEATHER-RESISTANT BIODEGRADABLE FILM, AND PREPARATION

METHOD AND USE THEREOF

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of degradable materials, in particular to a weather-resistant biodegradable film, and a preparation method and use thereof.

BACKGROUND

[0002] Biodegradable plastics are new green materials that are expected to replace traditional plastics such as polyethylene and polystyrene and reduce "white pollution”.

The biodegradable plastics have a wide range of sources and various properties, and can meet the needs of various uses in production and life. Moreover, after use, the biodegradable plastics can be decomposed into carbon dioxide and water by microorganisms in the environment, thus effectively avoiding environmental pollution.

[0003] However, biodegradable plastic products are prone to aging during use, thereby accelerating degradation, shortening the service life, and affecting the use effect. For example, when being used in agricultural production, the biodegradable film is prone to aging due to strong UV irradiation in the natural environment, causing severe breakage of molecular chains. As a result, various problems occurred in biodegradable films, such as rapid decrease in molecular weight and mechanical properties, enhanced hydrophilicity, intensified degradation, and shortened service life.

Moreover, field covering functions of the biodegradable films, including temperature increasing, soil moisture retention, and weed control, are lost, and cannot meet the growth needs of some crops. In most film-mulched planting areas in China, the biodegradable mulching film with a conventional thickness of about 10 um has a complete field coverage period of about 40 d to 60 d. However, many crops have a field safety coverage period longer than the above period, such as 100 d to 110 d for cotton, 70 d to 85 d for corn, and 70 d to 80 d for tobacco. Accordingly, conventional biodegradable mulching films are difficult to meet the needs of these crops.

[0004] In order to slow down the aging and premature degradation of the biodegradable films during use, light stabilization additives (including UV absorbers and anti-UV agents) are mainly used in the prior art, and are sometimes supplemented with antioxidants. For example, Patent CN104744898A provided a fully biodegradable film and a preparation method thereof. Patent CN109535675A provided a hydrolysis- resistant and UV photoaging-resistant biodegradable plastic mulching film and a preparation method thereof. Patent CN110117413A provided a degradable mulching film for plateau vegetable planting and a preparation method and use thereof. However, since a thickness of the film is generally only a few micrometers to tens of micrometers, the UV absorbers in the prior art have an extremely short optical path, and an insignificant UV absorbing effect. Moreover, the anti-UV agents in the prior art can only prolong the service life for a few days, and cannot well avoid the poor weather resistance of the biodegradable films.

SUMMARY

[0005] In view of this, an objective of the present disclosure is to provide a weather- resistant biodegradable film, and a preparation method and use thereof. In the present disclosure, the weather-resistant biodegradable film has a low degradation rate and desirable weather resistance in natural environments.

[0006] To achieve the above objective, the present disclosure provides the following technical solutions:

[0007] The present disclosure provides a weather-resistant biodegradable film, including the following raw materials in parts by weight:

[0008] biodegradable polyester 60 parts to 99.988 parts;

[0009] starch or modified starch 0 parts to 20 parts;

[0010] foamer 0.001 parts to 1 part;

[0011] cross-linking agent 0.01 parts to 2 parts;

[0012] photoinitiator 0.001 parts to 1 part;

[0013] UV stabilizer 0 parts to 2 parts;

[0014] antioxidant 0 parts to 2 parts;

[0015] plasticizer 0 parts to 2 parts;

[0016] lubricant 0 parts to 2 parts; and

[0017] color masterbatch 0 parts to 8 parts.

[0018] Preferably, the biodegradable polyester is one or more selected from the group consisting of polybutylene adipate co-terephthalate (PBAT), polybutylene succinate (PBS), polylactic acid (PLA), polypropylene carbonate (PPC), and polyhydroxyalkanoate (PHA).

[0019] Preferably, the foamer is one or more selected from the group consisting of p-

toluenesulfonyl semicarbazide, azodicarbonamide, N‚N'- dinitrosopentamethylenetetramine, and 4,4'-oxydibenzenesulfonyl hydrazide.

[0020] Preferably, the cross-linking agent is one or more selected from the group consisting of a peroxide cross-linking agent, an acrylamide cross-linking agent, azobisisobutyronitrile (AIBN), triallyl isocyanurate, triallyl cyanurate, and trimethylolpropane triallyl ether.

[0021] Preferably, the photoinitiator is one or more selected from the group consisting of an aryl diazonium salt photoinitiator, an aryl onium salt photoinitiator, an organic ketone photoinitiator, dibenzoyl, benzoyl oxime, and aminobenzoate.

[0022] Preferably, the UV stabilizer is one or more selected from the group consisting of a salicylate UV stabilizer, a benzoate UV stabilizer, a benzophenone UV stabilizer, a benzotriazole UV stabilizer, a hindered amine UV stabilizer, and a triazine UV stabilizer;

[0023] the antioxidant is one or more selected from the group consisting of a hindered phenol antioxidant, an amine antioxidant, a phosphite antioxidant, a thioether antioxidant, a triazine antioxidant, and a bisphenol monoacrylate antioxidant;

[0024] the plasticizer is one or more selected from the group consisting of a phthalate plasticizer, an adipate plasticizer, a citrate plasticizer, an epoxy derivative plasticizer, and a sulfonic acid derivative plasticizer; and

[0025] the lubricant is one or more selected from the group consisting of a fatty acid amide lubricant, a fatty acid ester lubricant, an alkane lubricant, a metal soap lubricant, a siloxane lubricant, and an inorganic powder lubricant.

[0026] The present disclosure further provides a preparation method of the weather- resistant biodegradable film, including the following steps:

[0027] (1) mixing the foamer, the cross-linking agent, and the photoinitiator with an organic solvent, and dissolving to obtain a mixed aid dispersion;

[0028] (2) mixing the mixed aid dispersion with the biodegradable polyester, and removing the organic solvent to obtain a mixed aid-wrapped biodegradable polyester; and

[0029] (3) conducting processing and molding on the mixed aid-wrapped biodegradable polyester and the remaining raw materials of the weather-resistant biodegradable film, to obtain the weather-resistant biodegradable film.

[0030] Preferably, in step (3), a method of the processing and molding specifically includes:

[0031] mixing the mixed aid-wrapped biodegradable polyester with the remaining raw materials of the weather-resistant biodegradable film, and conducting extrusion, granulation, and film blowing sequentially to obtain the weather-resistant biodegradable film;

[0032] alternatively:

[0033] subjecting the mixed aid-wrapped biodegradable polyester to extrusion and granulation sequentially, mixing obtained granules with the remaining raw materials of the weather-resistant biodegradable film, and conducting film blowing to obtain the weather-resistant biodegradable film.

[0034] Preferably, the extrusion refers to twin-screw extrusion conducted at 130°C to 195°C and a screw speed of 50 r/min to 250 r/min; and

[0035] the film blowing is conducted at 120°C to 180°C.

[0036] The present disclosure further provides use of the weather-resistant biodegradable film as an agricultural mulching film or a packaging material.

[0037] The present disclosure provides a weather-resistant biodegradable film, including the following raw materials in parts by weight: 80 parts to 99.988 parts of a biodegradable polyester, O parts to 20 parts of starch or modified starch, 0.001 parts to 1 part of a foamer, 0.01 parts to 2 parts of a cross-linking agent, 0.001 parts to 1 part of a photoinitiator, 0 parts to 2 parts of a UV stabilizer, O parts to 2 parts of an antioxidant, 0 parts to 2 parts of a plasticizer, 0 parts to 2 parts of a lubricant, and 0 parts to 8 parts of a color masterbatch. In the present disclosure, a foamer, a cross-linking agent, and a photoinitiator are added to raw materials. During processing, the foamer is decomposed by heat to generate tiny air bubbles, which wrap a part of the cross- In the inside the agent. The wrapped cross-linking agent does not react with the biodegradable polyester during the processing, and is uniformly dispersed in a processed biodegradable film as a protected auxiliary agent. During use, as the film degrades, the tiny air bubbles burst, releasing the cross-linking agent under protection.

Through an action of the photoinitiator, the cross-linking agent gradually undergoes cross-linking with the polyester, and can effectively slow down breakage of polyester molecular chains or partially re-ligate broken molecules. In this way, premature rupture of the biodegradable film is prevented and a degradation rate is slowed down.

During processing, the unwrapped cross-linking agent increases a molecular chain length of the biodegradable polyester. In this way, the molecular chains are laterally linked during the processing, and a three-dimensional network structure is strengthened, thereby improving the mechanical properties of a biodegradable mulching film. The results of the examples show that the weather-resistant biodegradable film has a longitudinal tensile force, a longitudinal elongation at break, a transverse tensile force, and a transverse elongation at break after aging that are not 5 significantly lower than those before the aging, and some properties are even better than those before the aging. A molecular weight polydispersity Mw/Mn is lower than that of the comparative examples. This indicates that the weather-resistant biodegradable film undergoes molecular reconnection during use. A water contact angle after the aging is increased instead, indicating that an aged biodegradable film has high hydrophobicity and is not easy to degrade in contact with water.

[0038] The present disclosure further provides a preparation method of the weather- resistant biodegradable film. In the present disclosure, the foamer, cross-linking agent, and photoinitiator are mixed with an organic solvent to obtain a mixed aid dispersion, and then the mixed aid dispersion is mixed with the biodegradable polyester. In this way, the foamer, cross-linking agent, and photoinitiator can be uniformly wrapped on a surface of the biodegradable polyester. This helps the tiny bubbles generated during processing to wrap the cross-linking agent, and a cross-linking reaction during use.

Meanwhile, the preparation method has simple operation and is suitable for industrial batch production.

[0039] The present disclosure further provides use of the weather-resistant biodegradable film as an agricultural mulching film. In the present disclosure, the weather-resistant biodegradable film has a low degradation rate and desirable weather resistance in natural environments. When being used as an agricultural mulching film, the film can maintain complete coverage during a critical period of crop growth, and maintain the functions of increasing temperature, retaining soil moisture, and preventing weeds during the covering,

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. | shows comparisons of a molecular weight Mw distribution before and after aging in Example 1;

[0041] FIG. 2 shows comparisons of a molecular weight Mw distribution before and after aging in Comparative Example 1;

[0042] FIG. 3 shows a water contact angle of a film before aging in Example 1;

[0043] FIG. 4 shows a water contact angle of a film after aging in Example 1;

[0044] FIG. 5 shows a water contact angle of a film before aging in Comparative

Example 1;

[0045] FIG. 6 shows a water contact angle of a film after aging in Comparative

Example 1;

[0046] FIG. 7 shows results of mulching for 55 d in a field test of sugar beet mulching and planting in Example 1 and Comparative Example 1; and

[0047] FIG. 8 shows results of mulching for 64 d in a field test of tobacco mulching and planting in Example 2 and Comparative Example 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The present disclosure provides a weather-resistant biodegradable film, including the following raw materials in parts by weight:

[0049] biodegradable polyester 60 parts to 99.988 parts;

[0050] starch or modified starch 0 parts to 20 parts;

[0051] foamer 0.001 parts to 1 part;

[0052] cross-linking agent 0.01 parts to 2 parts;

[0053] photoinitiator 0.001 parts to 1 part;

[0054] UV stabilizer 0 parts to 2 parts;

[0055] antioxidant 0 parts to 2 parts;

[0056] plasticizer 0 parts to 2 parts;

[0057] lubricant 0 parts to 2 parts; and

[0058] color masterbatch 0 parts to 8 parts.

[0059] Unless otherwise specified, the raw materials used in the present disclosure are all commercially available.

[0060] In the present disclosure, in parts by weight, the weather-resistant biodegradable film includes 60 parts to 99.988 parts, preferably 65 parts to 99.5 parts, more preferably 80 parts to 99 parts, and even more preferably 92 parts to 98 parts of the biodegradable polyester. In the present disclosure, the biodegradable polyester is preferably one or more selected from the group consisting of PBAT, PBS, PLA, PPC, and PHA, more preferably the PBAT.

[0061] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes O parts to 20 parts, preferably 1 part to 15 parts, and more preferably 5 parts to 10 parts of the starch or modified starch.

[0062] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes 0.001 parts to 1 part, preferably 0.005 parts to 0.8 parts, more preferably 0.01 parts to 0.6 parts, and even more preferably 0.05 parts to 0.5 parts of the foamer. The foamer is preferably one or more selected from the group consisting of p-toluenesulfonyl semicarbazide, azodicarbonamide, N‚N'-dinitrosopentamethylenetetramine, and 4,4'- oxydibenzenesulfonyl hydrazide.

[0063] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes 0.01 parts to 2 parts, preferably 0.05 parts to 1.5 parts, more preferably 0.1 parts to 1.2 parts, and even more preferably 0.2 parts to 0.8 parts of the cross-linking agent. The cross-linking agent is preferably one or more selected from the group consisting of a peroxide cross-linking agent, an acrylamide cross-linking agent, AIBN, triallyl isocyanurate, triallyl cyanurate, and trimethylolpropane triallyl ether. The peroxide cross-linking agent includes preferably one or more of dicumyl peroxide, dicumyl di-tert-butyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, benzoyl peroxide, peroxide lauroyl, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, and 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane. The acrylamide cross-linking agent includes preferably N-methylolacrylamide and/or N,N- dimethylbisacrylamide.

[0064] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes 0.001 parts to 1 part, preferably 0.005 parts to 0.8 parts, more preferably 0.01 parts to 0.5 parts, and even more preferably 0.01 parts to 0.4 parts of the photoinitiator. The photoinitiator is preferably one or more selected from the group consisting of an aryl diazonium salt photoinitiator, an aryl onium salt photoinitiator, an organic ketone photoinitiator, dibenzoyl, benzoyl oxime, and aminobenzoate. The aryl onium salt photoinitiator includes preferably one or more of aryl iodonium salts, diaryl iodonium salts, alkylaryl iodonium salts, aryl sulfonium salts, triaryl sulfonium salts, diaryl bromonium salts, and triaryl selenonium salts. The organic ketone photoinitiator includes preferably one or more of benzophenone, acetophenone, benzyl ketal, aminoketone, hydroxyketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone.

[0065] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes O parts to 2 parts,

preferably 0.1 parts to 1.5 parts, and more preferably 0.2 parts to 1 part of the UV stabilizer. The UV stabilizer is preferably one or more selected from the group consisting of a salicylate UV stabilizer, a benzoate UV stabilizer, a benzophenone UV stabilizer, a benzotriazole UV stabilizer, a hindered amine UV stabilizer, and a triazine

UV stabilizer. The salicylate UV stabilizer is preferably p-tert-octylphenyl salicylate (OPS). The benzoate UV stabilizer is preferably 3,5-di-tert-butyl-4-hydroxybenzoic acid-2,4-di-tert-butylphenyl ester (UV-120). The benzophenone UV stabilizer is preferably 2-hydroxyl-4-n-octyloxybenzophenone (UV-531) or 2-hydroxyl-4- methoxybenzophenone (UV-9). The benzotriazole UV stabilizer preferably includes one or more of 2'-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (UV-326), 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole (UV-329), 2-(2'-hydroxy- 3',5'-di-t-butylphenyl)-5-chlorobenzotriazole (UV-327), and 2-[2-hydroxy-3,5-di-(1,1- dimethylbenzyl) phenyl]-2H-benzotriazole (UV-328). The hindered amine UV stabilizer includes preferably one or more of a polymer of succinic acid with 4- hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (such as BW-10LD or

Tinuvin622LD), a polymer of 1,6-hexamethylenediamine\2,2,6,6- tetramethylpiperidinamine\tert-octylamineitripolyfluorine chloride (944), bis(2,2,6,6,- tetramethylpiperidinyl) sebacate (770), light stabilizer 783 (50% of 622 + 50% of 944).

The triazine UV stabilizer is preferably 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxy- phenol (1577).

[0066] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes O parts to 2 parts, preferably 0.1 parts to 1.5 parts, and more preferably 0.2 parts to 1 part of the antioxidant. The antioxidant is preferably one or more selected from the group consisting of a hindered phenol antioxidant, an amine antioxidant, a phosphite antioxidant, a thioether antioxidant, a triazine antioxidant, and a bisphenol monoacrylate antioxidant. The hindered phenol antioxidant includes preferably pentaerythritol tetrakis(B-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (1010), 2,6- di-tert-butyl-4-methylphenol (264). The phosphite antioxidant includes preferably tris(nonylphenyl)phosphite (TNP) and/or tris[2,4-di-tert-butylphenyl]phosphite (168).

The thioether antioxidant is preferably distearyl thiodipropionate (DSTP). The triazine antioxidant includes preferably tris[2-(3,5-di-tert-butyl-4-hydroxyphenyl)- propionyloxyethyl]isocyanate (3125), 2-(4-hydroxy-3,5-di-tert-butylanilino)-4,6-bis(n- octylthio)-1,3,5-triazine (565).

[0067] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes O parts to 2 parts, preferably 0.1 parts to 1.5 parts, and more preferably 0.2 parts to 1 part of the lubricant.

The lubricant is preferably one or more selected from the group consisting of a fatty acid amide lubricant, a fatty acid ester lubricant, an alkane lubricant, a metal soap lubricant, a siloxane lubricant, and an inorganic powder lubricant. The fatty acid amide lubricant includes preferably one or more of ethylene bis(stearamide) (EBS), erucamide, and oleamide. The fatty acid ester lubricant is preferably glycerol monostearate (GMS). The alkane lubricant (also known as paraffin lubricant) is preferably white oil and/or polyethylene wax. The metal soap lubricant includes preferably calcium stearate and/or magnesium stearate. The siloxane lubricant is preferably polydimethylsiloxane. The inorganic powder lubricant includes preferably one or more of talcum powder, silica, nano-silica, and mica. The lubricant has a particle size of preferably 20 nm to 20 um, more preferably 100 nm to 8 um.

[0068] In the present disclosure, based on the parts by weight of the biodegradable polyester, the weather-resistant biodegradable film includes O parts to 8 parts, preferably 1 part to 7 parts, and more preferably 2 parts to 5 parts of the color masterbatch. The color masterbatch is preferably carbon black; the color masterbatch does not contain polyolefins or other non-biodegradable polyesters.

[0069] In the present disclosure, the weather-resistant biodegradable film is preferably a weather-resistant biodegradable mulching film.

[0070] In the present disclosure, the weather-resistant biodegradable film has a thickness of preferably 3 pm to 100 um, more preferably 4 um to 60 um, and even more preferably 5 um to 40 um.

[0071] The present disclosure further provides a preparation method of the weather- resistant biodegradable film, including the following steps:

[0072] (1) mixing the foamer, the cross-linking agent, and the photoinitiator with an organic solvent, and dissolving to obtain a mixed aid dispersion;

[0073] (2) mixing the mixed aid dispersion with the biodegradable polyester, and removing the organic solvent to obtain a mixed aid-wrapped biodegradable polyester; and

[0074] (3) conducting processing and molding on the mixed aid-wrapped biodegradable polyester and the remaining raw materials of the weather-resistant biodegradable film, to obtain the weather-resistant biodegradable film.

[0075] In the present disclosure, the foamer, the cross-linking agent, and the photoinitiator are mixed with an organic solvent, and dissolved to obtain a mixed aid dispersion. The organic solvent includes preferably one or more of methanol, ethanol, propanol, isopropanol, butanol, hexanediol, acetone, butanone, 1,1-dichloroethane, 1,1,1-trichloroethane, ethyl acetate, butyl acetate, and cyclohexane, more preferably the ethanol. The foamer, cross-linking agent, and photoinitiator are dissolved in the organic solvent and then coated on a surface of the biodegradable polyester particles to form a thin layer, rather than being mixed in the form of small particles with the biodegradable polyester particles. On the one hand, this enables the homogeneous mixing of the three additives, such that they can work efficiently. On the other hand, the thin layer can avoid the instability of the film blowing caused by the foamer due to violent foaming, and can also reduce material defects the foamer may cause to the polyester during processing. A total mass of the foamer, cross-linking agent, and photoinitiator and a volume of the organic solvent are at a ratio of preferably 1:50.

[0076] In the present disclosure, the mixing is preferably conducted by spraying or stirring. There is no special requirement on a specific operation mode of the spraying or stirring.

[0077] In the present disclosure, the mixed aid dispersion is mixed with the biodegradable polyester, and the organic solvent is removed to obtain a mixed aid- wrapped biodegradable polyester. The mixing is preferably conducted by stirring. The stirring is conducted at preferably 20 r/min to 2,500 r/min, more preferably 100 r/min to 1,000 r/min for preferably 0.5 min to 10 min, more preferably 2 min to 6 min, and even more preferably 5 min.

[0078] In the present disclosure, there is no special requirement on a way of removing the organic solvent, and the way of removing the organic solvent well known to those skilled in the art can be used.

[0079] In the present disclosure, processing and molding is conducted on the mixed aid-wrapped biodegradable polyester and the remaining raw materials of the weather- resistant biodegradable film, to obtain the weather-resistant biodegradable film. The processing and molding includes preferably the following steps:

[0080] mixing the mixed aid-wrapped biodegradable polyester with the remaining raw materials of the weather-resistant biodegradable film, and conducting extrusion, granulation, and film blowing sequentially to obtain the weather-resistant biodegradable film.

[0081] In the present disclosure, the mixing is preferably melt blending, and the melt blending is preferably conducted in a twin-screw extruder. The extrusion preferably refers to twin-screw extrusion conducted at preferably 130°C to 195°C, more preferably 150°C to 180°C and a screw speed of preferably 50 r/min to 350 r/min, more preferably 100 r/min to 200 r/min.

[0082] In the present disclosure, cooling is preferably conducted before the granulation after the extrusion. The cooling preferably refers to air cooling or water cooling, more preferably the air cooling; a material temperature after the cooling is preferably 20°C to 30°C. The granulation preferably refers to granulator granulation.

After the granulation, obtained granules have a diameter of preferably 2 mm to 6 mm, more preferably 2 mm to 4 mm and a length of preferably 1 mm to 10 mm, more preferably 3 mm to 6 mm.

[0083] In the present disclosure, the film blowing is preferably conducted using a single-screw extruder or a twin-screw extruder. The film blowing is conducted at preferably 120°C to 180°C, more preferably 140°C to 160°C.

[0084] The processing and molding includes further preferably the following steps:

[0085] subjecting the mixed aid-wrapped biodegradable polyester to extrusion and granulation sequentially, mixing obtained granules with the remaining raw materials of the weather-resistant biodegradable film, and conducting film blowing to obtain the weather-resistant biodegradable film.

[0086] In the present disclosure, specific operation modes of the extrusion, the granulation, and the film blowing are preferably the same as above, and will not be repeated here.

[0087] The present disclosure further provides use of the weather-resistant biodegradable film as an agricultural mulching film or a packaging material. The weather-resistant biodegradable film is preferably used for mulching and planting of peanuts, sugar beets, corn, garlic, processed tomatoes, rice, or tobacco. In the present disclosure, the weather-resistant biodegradable film has a low degradation rate and desirable weather resistance in natural environments. When being used as an agricultural mulching film, the film can maintain complete coverage during a critical period of crop growth, and maintain the functions of increasing temperature, retaining soil moisture, and preventing weeds during the covering.

[0088] In the present disclosure, the packaging material includes preferably one or more of food packaging bags, plastic wraps, shopping bags, and express bags. The weather-resistant biodegradable film has low degradation rate and desirable weather resistance, and can improve a service life of the packaging material when being used as a degradable packaging material.

[0089] The weather-resistant biodegradable film, and the preparation method and the use thereof provided by the present disclosure will be described in detail in connection with the following examples, but they should not be construed as limiting the protection scope of the present disclosure.

[0090] Example 1

[0091] A high-weather-resistant biodegradable film and a preparation method thereof were provided, where raw materials were as follows in parts by weight:

[0092] PBAT 97.99 parts;

[0093] foamer 0.4 parts;

[0094] cross-linking agent 0.5 parts;

[0095] photoinitiator 0.01 parts;

[0096] UV stabilizer 0.5 parts; and

[0097] lubricant 0.6 parts.

[0098] The foamer was azodicarbonamide. The cross-linking agent was dicumyl peroxide. The photoinitiator was benzyl ketal. The UV stabilizer included 2-(2'- hydroxy-5'-tert-octylphenyl)benzotriazole (UV-329) and a polymer of 1,6- hexamethylenediamine\2,2,6,6-tetramethylpiperidinamine'tert- octylamine\tripolyfluorine chloride (944), mixed at a mass ratio of 1:1. The lubricant was EBS.

[0099] Example 2

[0100] A high-weather-resistant biodegradable film and a preparation method thereof were provided, where raw materials were as follows in parts by weight:

[0101] PBAT 82.095 parts,

[0102] PPC 8 parts;

[0103] modified starch 5 parts;

[0104] foamer 0.3 parts;

[0105] cross-linking agent 0.8 parts;

[0106] photoinitiator 0.005 parts;

[0107] UV stabilizer 0.8 parts;

[0108] antioxidant 0.6 parts;

[0109] plasticizer 1.2 parts; and

[0110] lubricant 1.2 parts.

[0111] The foamer was 4,4'-oxydibenzenesulfonyl hydrazide. The cross-linking agent was diisopropyl peroxydicarbonate. The photoinitiator was 2-methyl-1-[4- (methylthio)phenyl]-2-morpholino-1-propanone. The UV stabilizer included a polymer of 1,6-hexamethylenediamine\2,2,6,6-tetramethylpiperidinamine\tert- octylamine\tripolyfluorine chloride and a polymer of succinic acid with 4-hydroxy- 2,2,6,6-tetramethyl-1-piperidineethanol (783). The antioxidant was a mixture of 2,6-di- tert-butyl-4-methylphenol (264) and pentaerythritol tetrakis(B-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate) (1010) at a mass ratio of 1:1. The plasticizer was tributyl citrate. The lubricant included erucamide and calcium stearate with a mass ratio of 1:2.

[0112] Example 3

[0113] A high-weather-resistant biodegradable film and a preparation method thereof were provided, where raw materials were as follows in parts by weight:

[0114] PBAT 97.7 parts;

[0115] foamer 0.5 parts;

[0116] cross-linking agent 0.5 parts;

[0117] photoinitiator 0.5 parts; and

[0118] lubricant 0.8 parts.

[0119] The foamer was azodicarbonamide. The cross-linking agent included N- methylolacrylamide and dicumyl peroxide at a mass ratio of 3:1. The photoinitiator was benzophenone. The lubricant included oleamide and low-molecular-weight polyethylene wax with a mass ratio of 1:1.

[0120] Example 4

[0121] A high-weather-resistant biodegradable film and a preparation method thereof were provided, where raw materials were as follows in parts by weight:

[0122] PBAT 94.8 parts;

[0123] foamer 0.2 parts;

[0124] cross-linking agent 0.5 parts;

[0125] photoinitiator 0.2 parts;

[0126] UV stabilizer 0.3 parts;

[0127] antioxidant 0.2 parts;

[0128] lubricant 0.8 parts; and

[0129] color masterbatch 3 parts.

[0130] The foamer was p-toluenesulfonyl semicarbazide. The cross-linking agent was

2,5-dimethyl-2,5-di-tert-butyl peroxyhexane. The photoinitiator was bis(4-tert- butylphenyl)iodonium hexafluorophosphate. The UV stabilizer was bis(2,2,6,6,- tetramethylpiperidinyl) sebacate (770). The antioxidant was 2-(4-hydroxy-3,5-di-tert- butylanilino)-4,6-bis(n-octylthio)-1,3,5-triazine (565). The lubricant was talcum powder. The color masterbatch was carbon black, did not contain polyolefins or other non-biodegradable polyesters, and had a content of 50%.

[0131] Comparative Example 1

[0132] A biodegradable film and a preparation method thereof were provided, where raw materials were as follows in parts by weight:

[0133] PBAT 98.5 parts;

[0134] foamer 0.4 parts;

[0135] UV stabilizer 0.5 parts;

[0136] lubricant 0.6 parts.

[0137] Compared with Example 1, this comparative example did not contain the cross-linking agent and the photoinitiator. The kinds of the foamer, the UV stabilizer, and the lubricant of this comparative example were identical with those in Example 1.

[0138] Comparative Example 2

[0139] A biodegradable film and a preparation method thereof were provided, where raw materials were as follows in parts by weight:

[0140] PBAT 98.39 parts;

[0141] cross-linking agent 0.5 parts;

[0142] photoinitiator 0.01 parts;

[0143] UV stabilizer 0.5 parts; and

[0144] lubricant 0.6 parts.

[0145] Compared with Example 1, this comparative example did not contain the foamer. The kinds of the cross-linking agent, the photoinitiator, the UV stabilizer, and the lubricant of this comparative example were identical with those in Example 1.

[0146] Comparative Example 3

[0147] A biodegradable film and a preparation method thereof were provided, where raw materials were as follows in parts by weight:

[0148] PBAT 83.2 parts;

[0149] PPC 8 parts;

[0150] modified starch 5 parts;

[0151] UV stabilizer 0.8 parts;

[0152] antioxidant 0.6 parts;

[0153] plasticizer 1.2 parts; and

[0154] lubricant 1.2 parts.

[0155] Compared with Example 2, this comparative example did not contain the foamer, the cross-linking agent, and the photoinitiator. The kinds of the UV stabilizer, the antioxidant, the plasticizer, and the lubricant of this comparative example were identical with those in Example 2.

[0156] A preparation method of Examples 1 to 5 and Comparative Examples 1 to 3 included the following steps:

[0157] (1) the foamer, the cross-linking agent, and the photoinitiator were mixed with ethanol, to obtain a mixed aid dispersion (if one or more of the foamer, the cross- linking agent, and the photoinitiator was not included, the addition was omitted);

[0158] (2) the mixed aid dispersion was mixed with the biodegradable polyester by spray drying, and the solvent ethanol was completely volatilized to obtain a mixed aid- wrapped biodegradable polyester;

[0159] (3) the mixed aid-wrapped biodegradable polyester and remaining raw materials of the weather-resistant biodegradable film were mixed in a mixer at 200 r/min for 5 min; a resulting mixed material was put into a twin-screw extruder to conduct melt blending at 130°C to 195°C and a screw speed of 150 r/min; an obtained product was cooled to 20°C by air cooling, and pelletized by a pelletizer to obtain masterbatches with a diameter of 2 mm to 4 mm and a length of 3 mm to 6 mm; and

[0160] (4) the masterbatches were subjected to film blowing by multi-layer co- extrusion with a twin-screw extrusion film blowing machine at a processing temperature of the screw of 120°C to 180°C, to obtain a biodegradable film with a thickness of 10.0 um+1.0 um.

[0161] Comparative Example 4

[0162] The raw material types and dosages of Comparative Example 4 were the same as those in Example 1. The difference was that a preparation method included the following steps:

[0163] all raw materials of the weather-resistant biodegradable film were mixed in a mixer at 200 r/min for 5 min; a resulting mixed material was put into a twin-screw extruder to conduct melt blending at 130°C to 195°C and a screw speed of 150 r/min; an obtained product was cooled to 20°C by air cooling, and pelletized by a pelletizer to obtain masterbatches with a diameter of 2 mm to 4 mm and a length of 3 mm to 6 mm;

and

[0164] the masterbatches were subjected to film blowing by multi-layer co-extrusion with a twin-screw extrusion film blowing machine at a processing temperature of the screw of 120°C to 180°C, to obtain a biodegradable film with a thickness of 10.0 pum*l1.0 um.

[0165] The performances of the biodegradable films obtained in Examples 1 to 4 and

Comparative Examples 1 to 4 were tested, and the results were shown in Table 1.

[0166] Table 1 Performance test results“ of biodegradable films obtained in Examples 1 to 4 and Comparative Examples 1 to 4

[0167]

Mw

Example l | Before 4.00 369 3.03 594 80619 2.46 101.2 me | [RR]

After 3.68 337 3.09 480 55829 2.76 102.8 ome I I lI al

Example 2 | Before 410 315 3.80 630 89414 2.42 102.2 ee]

After 4.30 342 2.93 439 61944 2.87 104.7

Example 3 Before 3.63 329 3.49 636 86353 2.46 98.5 ee

After 3.85 327 3.14 462 51052 2.83 101.9 we]

Example 4 Before 3.33 306 2.63 514 83133 2.12 103.4 me | [LRTI

After 3.53 343 2.31 477 52794 2.87 106.2 we I I ll al

Comparati Before 3.88 331 3.31 580 81297 2.16 103.3

Example I | After 2.88 287 1.89 343 32999 331 96.4

Comparati Before 3.93 394 3.29 612 86913 1.95 103.9

Example 2 After 2.93 316 2.23 337 32467 3.22 953 ae | | TE

Comparati Before 4.03 291 3.43 539 83654 2.12 101.2

Example 3 | After 2.63 265 1.54 281 30444 313 90.9

I EE Il i il

Comparati Before 3.46 376 3.21 527 82366 201 102.9

Example 4 After 2.77 255 1.82 248 32475 3.37 94.4 me]

[0168] Note:

[0169] a: The tests of transverse and longitudinal tensile forces and elongations at break in the table were conducted according to GB/T 35795-2017 "Biodegradable mulching film for agricultural uses".

[0170] b: Mw represented the weight average molecular weight; Mn represented the number average molecular weight; and Mw/Mn represented the molecular weight polydispersity, that is, a ratio of the weight average molecular weight to the number average molecular weight. The larger the Mw/Mn was, the wider the molecular weight distribution was.

[0171] c: The contact angle 8 was an angle between a solid-liquid interface to a gas- liquid interface through a liquid interior at the junction of the film, water droplets, and air. The smaller the angle was, the better the hydrophilicity of the film was, and the easier the film was to degrade in contact with moisture in the environment.

[0172] d: The aging referred to artificially accelerated aging. A test method was conducted in accordance with the provisions of GB/T 16422.2-2014 "Plastics--

Methods Of Exposure To Laboratory Light Sources--Part 2: Xenon-Arc Sources": an irradiation method adopted a method A, with an irradiance of narrow-band (340 nm) 0.51 W/(m? nm); a temperature control method used a black label thermometer; an exposure cycle method used cycle number 1, with a duration of 100 h.

[0173] The comparisons of molecular weight Mw distribution before and after aging in Example 1 were shown in FIG. 1, and the comparisons of molecular weight Mw distribution before and after aging in Comparative Example 1 were shown in FIG. 2.As shown in FIG. 1 and FIG. 2, the average molecular weight of the film in

Comparative Example | decreased significantly after aging. However, after aging the film of Example 1, the average molecular weight was substantially the same as that before aging.

[0174] In Example 1, the water contact angle of the film before aging was shown in

FIG. 3, and the two figures in FIG. 3 were two parallel tests. The water contact angle of the film after aging was shown in FIG. 4, and the two figures in FIG. 4 were two parallel tests. In Comparative Example 1, the water contact angle of the film before aging was shown in FIG. 5, and the two figures in FIG. 5 were two parallel tests. The water contact angle of the film after aging was shown in FIG. 6, and the two figures in

FIG. 6 were two parallel tests. As shown in FIG. 3 to FIG. 6, the contact angle of the film in Comparative Example 1 became smaller after aging, indicating that the hydrophilicity was enhanced and the film was more likely to biodegrade. However,

after the film in Example 1 was aged, the contact angle increased instead, the hydrophilicity decreased, and the film was not easy to degrade.

[0175] Use Example 1

[0176] The biodegradable films obtained in Examples 1 to 4 and Comparative

Examples 1 to 4 were used as agricultural mulching films for the mulching and planting of peanut, sugar beet, corn, garlic, processed tomato, rice, and tobacco. The coverage of the 8 kinds of films was monitored by means of regular survey. A monitoring method was as follows: field investigation was conducted every 7 d (every 3 d when covering 30 d to 70 d), and 0.4 mx5 m of the film was randomly selected for each treatment. When three or more holes with a diameter of 3 cm or more or cracks with a length of 10 cm or more appeared on a film surface, it was determined that the film began to degrade and the full coverage period ended. The complete field coverage periods of the biodegradable films obtained in Examples 1 to 4 and Comparative

Examples 1 to 4 for different crops were shown in Table 2.

[0177] Table 2 Complete field coverage period of biodegradable films obtained in

Examples 1 to 4 and Comparative Examples 1 to 4

[0178]

Mulching crop Complete coverage period/days

Bape

Emi 3

Eagle 3

Gol

Eamie Processed tio

Compare Example 1

Tobacco 40

Compare Example

Comparative Example 4 52 9

[0179] When the biodegradable films obtained in Example 1 and Comparative

Example 1 were used as an agricultural mulching film for the mulching and planting of sugar beet, the real picture after 55 d of mulching was shown in FIG. 7. As shown in

FIG. 7, the biodegradable film obtained in Example 1 had no obvious signs of degradation, while the biodegradable film obtained in Comparative Example 1 already had relatively obvious holes and large cracks.

[0180] When the biodegradable films obtained in Example 2 and Comparative

Example 3 were used as an agricultural mulching film for the mulching and planting of tobacco, the real picture after 64 d of mulching was shown in FIG. 8. As shown in FIG. 8, the biodegradable film obtained in Example 2 had no obvious signs of degradation, while the biodegradable film obtained in Comparative Example 3 already had relatively obvious holes and large cracks.

[0181] The above are merely preferred implementations of the present disclosure. It should be noted that several improvements and modifications may further be made by a person of ordinary skill in the art without departing from the principle of the present disclosure, and such improvements and modifications should also be deemed as falling within the protection scope of the present disclosure.

Claims

Conclusions

1. Weatherproof biodegradable film, comprising the following raw materials in parts by weight: biodegradable polyester 60 parts-99,988 parts; starch or modified starch 0 parts-20 parts; foaming agent 0.001 parts-1 part; crosslinking agent 0.01 parts-2 parts; photoinitiator 0.001 parts-1 part, UV stabilizer O parts-2 parts; antioxidant O parts-2 parts; plasticizer 0 parts-2 parts; lubricant O parts-2 parts; and color masterbatch 0 parts-8 parts.

A weatherproof biodegradable film according to claim 1, wherein the biodegradable polyester is one or more selected from the group consisting of polybutylene adipate-co-terephthalate (PBAT), polybutylene succinate (PBS), polylactic acid (PLA), polypropylene carbonate (PPC) and polyhydroxyalkanoate (PHA).

A weather-resistant biodegradable film according to claim 1 or 2, wherein the blowing agent is one or more selected from the group consisting of p-toluenesulfonyl semicarbazide, azodicarbonamide, N,N'-dinitrosopentamethylenetetramine and 4,4'-oxydibenzenesulfonyl hydrazide.

A weatherproof biodegradable film according to claim 1 or 2, wherein the crosslinking agent is one or more selected from the group consisting of a peroxide crosslinking agent, an acrylamide crosslinking agent, azobisisobutyronitrile (AIBN), triallyl isocyanurate, triallyl cyanurate and trimethylolpropane triallyl ether.

A weatherproof biodegradable film according to claim 1 or 2, wherein the photoinitiator is one or more selected from the group consisting of an aryldiazonium salt photoinitiator, an arylonium salt photoinitiator, an organic ketone photoinitiator , dibenzoyl, benzoyloxime and aminobenzoate.

A weatherproof biodegradable film according to claim 1, wherein the UV stabilizer is one or more selected from the group consisting of a salicylate UV stabilizer, a benzoate UV stabilizer, a benzophenone UV stabilizer, a benzotriazole UV stabilizer , a hindered amine UV stabilizer and a triazine UV stabilizer; the antioxidant is one or more selected from the group consisting of a hindered phenolic antioxidant, an amine antioxidant, a phosphite antioxidant, a thioether antioxidant, a triazine antioxidant and a bisphenol monoacrylate antioxidant; the plasticizer is one or more selected from the group consisting of a phthalate plasticizer, an adiate plasticizer, a citrate plasticizer, an epoxy derivative plasticizer and a sulfonic acid derivative plasticizer; and the lubricant is one or more selected from the group consisting of a fatty acid amide lubricant, a fatty acid ester lubricant, an alkane lubricant, a metal soap lubricant, a siloxane lubricant and an inorganic powder lubricant.

A method of preparing the weatherproof biodegradable film according to any one of claims 1 to 6, which comprises the steps of: (1) mixing the foaming agent, the crosslinking agent and the photoinitiator with an organic solvent and dissolving to form a mixed vehicle dispersion to obtain; (2) mixing the mixed vehicle dispersion with the biodegradable polyester and removing the organic solvent to obtain a mixed vehicle coated biodegradable polyester; and (3) carrying out processing and forming on the mixed aid coated biodegradable polyester and the remaining raw materials of the weatherproof biodegradable film, to obtain the weatherproof biodegradable film.

Preparation method according to claim 7, wherein in step (3), a method for processing and shaping in particular comprises the following:

mixing the mixed aid coated biodegradable polyester with the remaining raw materials of the weatherproof biodegradable film and successively performing extrusion, granulation and film blowing to obtain the weatherproof biodegradable film; alternatively: successively subjecting the mixed aid coated biodegradable polyester to extrusion and granulation, mixing the obtained granules with the remaining raw materials of the weatherproof biodegradable film, and performing film blowing to obtain the weatherproof biodegradable film.

Preparation method according to claim 8, wherein the extrusion involves twin-screw extrusion carried out at 130°C-195°C and a screw speed of 50 rpm-250 rpm; and film blowing is carried out at 120°C-180°C.

Use of the weather-resistant biodegradable film according to any one of claims 1 to 6 or a weather-resistant biodegradable film prepared by the preparation method according to any one of claims 7 to 9 as an agricultural mulch layer or a packaging material.