A non-starch-based biodegradable polyethylene film and its preparation method

Abstract

This invention belongs to the field of film production technology, specifically relating to a non-starch-based biodegradable polyethylene film and its preparation method. The non-starch-based biodegradable polyethylene film comprises the following raw materials in parts by weight: 30-50 parts LDPE, 30-50 parts LLDPE, 5-20 parts HDPE, 0.1-0.8 parts photosensitive system, and 0.5-4 parts biodegradable system. This invention uses polyethylene resin as the base material, combined with a specific photosensitive system and biodegradable system, and is prepared using a masterbatch method and a direct method. A floating dyeing process ensures uniform dispersion of additives, and a standardized blown film and thickness control process ensures that the resulting film requires no starch filler. It possesses mechanical properties that meet application requirements and achieves a synergistic effect of photodegradation and biodegradation. After field use, it gradually and completely degrades, avoiding soil pollution, thus balancing practicality and environmental friendliness.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of film production, and particularly relates to a non-starch type biodegradable polyethylene film and a preparation method thereof. BACKGROUND

[0002] Polyethylene (PE) film is widely used in agricultural mulching film, packaging material and other fields due to its light weight, strong weather resistance and low cost, among which the annual consumption of agricultural mulching film is particularly large, which effectively promotes crop yield and income. However, the polyethylene molecular chain structure is stable and has strong anti-degradation ability, and it is difficult to decompose in the natural environment after being discarded, which can remain in the soil or environment for a long time, resulting in soil compaction, reduced air permeability, and destruction of the ecological balance, which has become a key bottleneck restricting the sustainable development of agriculture and environmental protection.

[0003] In order to solve the degradation problem of polyethylene film, various degradation modification schemes have been developed in the prior art, and the technology of using natural high molecular compound starch as a microbial culture medium is relatively common. However, due to the incompatibility of starch and PE, the hygroscopicity of starch is very strong, and the starch particles are coarse. If the final product of agricultural mulching film with extremely harsh use conditions is to be made, there will be a sharp contradiction in technology and economic cost. Therefore, it is urgent to research a non-starch type biodegradable polyethylene film and a preparation method thereof, so that it is controllable and ultra-thin, and can achieve the purpose of increasing crop yield and income, and then rapidly degrades in the environment. SUMMARY

[0004] In view of the defects of the prior art, the application provides a non-starch type biodegradable polyethylene film and a preparation method thereof. The application uses polyethylene resin as a base material, matches a specific photosensitive system, a biodegradable system and a dispersing agent, and is prepared by a master batch method or a direct method. The auxiliary agent is uniformly dispersed through a dyeing process, and the standardization of the film blowing and thickness control process is matched. The obtained film does not need to be filled with starch, has mechanical properties meeting the application requirements, and can realize the synergistic effect of photodegradation and biodegradation. The degradation induction period can be flexibly adjusted according to the crop growth demand and regional environmental characteristics. After being used in the field, it can be completely degraded, avoiding soil residue pollution, and taking into account the practicability and environmental protection. The application solves the problems of the existing starch-based degradation film, such as insufficient mechanical strength, poor water resistance, and easy residual polyethylene fragments after degradation, and the defects of the ordinary non-starch degradation film, such as poor application adaptability, incomplete degradation, and difficult to adjust the induction period.

[0005] The application provides a non-starch biodegradable polyethylene film, which comprises the following raw materials in parts by weight: 10-60 parts of LDPE (low-density polyethylene), 30-50 parts of LLDPE (linear low-density polyethylene), 5-20 parts of HDPE (high-density polyethylene), 0.01-0.8 parts of a photosensitive system, 0.5-4 parts of a biodegradation system, and 0.1-3 parts of a dispersant.

[0006] Preferably, the photosensitive system is an organic iron compound selected from one or more of acetylferrocene, cyclohexenylferrocene, n-octylferrocene, butyric acid butyl ester ferrocene, acetylacetone iron and benzoylferrocene.

[0007] Preferably, the biodegradation system comprises an organic amide compound and an inorganic phosphate compound.

[0008] Preferably, the dispersant is at least one of polyethylene wax and oxidized polyethylene wax.

[0009] The non-starch biodegradable polyethylene film is prepared by a master batch method or a direct method.

[0010] The application further provides a method for preparing the non-starch biodegradable polyethylene film by the master batch method, which specifically comprises the following steps:

[0011] S1, the photosensitive system, the biodegradation system and the dispersant are weighed, and are placed in a stainless steel mixer, mixed at room temperature for 10-15 min until uniform, and a mixed material I is formed;

[0012] S2, part of the LDPE is weighed and put into a high-speed stirrer, the mixed material I obtained in step S1 is added, the high-speed stirrer is started, and 1-3% of the mixed material I of a volatile organic solvent is sprayed at the same time, high-speed stirring is carried out for 3-5 min, and a premix is obtained;

[0013] S3, the premix is sent into a double-screw extrusion granulator, the processing temperature is controlled to be 130-180 DEG C, and melting mixing, extrusion, cooling and granulation are carried out, and a light biodegradable master batch is obtained;

[0014] S4, the LLDPE, the HDPE and the remaining part of the LDPE are weighed and added to the light biodegradable master batch, and the two are dry-mixed in the mixer for 5-10 min until uniform, and a mixed material II is formed;

[0015] S5, the mixed material II is put into the hopper of the film blowing machine, and the material is plasticized by melting through the following temperature gradient in the extruder: feeding section: 160-170 DEG C, compression section: 170-180 DEG C, homogenization section: 180-190 DEG C, head die: 175-185 DEG C, so that the molten material is obtained, then the molten material is extruded vertically upwards through the annular die to form a tubular blank, compressed air is injected into the tubular blank, the blowing ratio is controlled to be 2-3, the film is drawn by the traction roller, and the bubble tube after blowing is cooled and shaped by the cold air blown by the cooling air ring to form a stable frost line;

[0016] S6, the thickness of the film is measured online in real time by using a micrometer, and the thickness error is strictly controlled within ±1 micrometer, in the production workshop, the film sample with an area of 1m 2 is randomly cut and placed on a balance to weigh, for the degradable mulch film with a nominal thickness of 0.008mm, the weight is controlled to be 7.0-7.5g / m 2 , for the ultra-micro degradable mulch film with a nominal thickness of 0.005mm, the weight is controlled to be 4.5-5.0g / m 2 , and a non-starch biodegradable polyethylene film is obtained.

[0017] Further, the volatile organic solvent is anhydrous ethanol or acetone.

[0018] The application also provides a method for preparing a non-starch biodegradable polyethylene film by using a direct method, comprising the following steps:

[0019] Y1, the photosensitive system, the biodegradable system and the dispersing agent are weighed and placed in a stainless steel mixer, mixed at room temperature for 10-15 minutes until uniform, and mixed material III is formed;

[0020] Y2, in the high-speed mixer, all the weight parts of LDPE, LLDPE and HDPE are pre-placed, then the mixed material III is added, the machine is started, and the volatile anhydrous ethanol is sprayed at the same time, the amount is about 1-3% of the total weight of the solid, high-speed stirring for 5 min, the auxiliary agent is uniformly distributed on the surface of the resin, and then the material is discharged, and the direct film-out mixed material is obtained;

[0021] Y3. The direct film-forming mixture obtained in step Y2 is directly fed into the hopper of the blown film extruder. The material is melted and plasticized in the extruder through the following temperature gradients: feeding section: 160-170 ℃, compression section: 170-180 ℃, homogenization section: 180-190 ℃, die head: 175-185 ℃, resulting in molten material. This molten material is then extruded vertically upwards through a ring die to form a tubular preform. Compressed air is injected into the preform, controlling the blow-up ratio at 2-3. The film is then drawn into shape by traction rollers. The inflated bubble tubes are cooled and shaped by cold air blown from a cooling air ring, forming a stable frosting line. The film thickness is measured online in real time using a micrometer, with the thickness error strictly controlled within ±1 micrometer. In the production workshop, a 1m² area is randomly cut. 2 The membrane sample was placed on a balance and weighed. For a degradable mulch film with a nominal thickness of 0.008 mm, the weight should be controlled between 7.0 and 7.5 g / m³. 2 For ultra-micro degradable mulch films with a nominal thickness of 0.005 mm, their weight should be controlled between 4.5-5.0 g / m². 2 A non-starch-based biodegradable polyethylene film was obtained.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0023] (1) The mechanical properties of the non-starch type biodegradable polyethylene film prepared by the present invention are good. The amount of photobiodegradable additives used for PE modification is small. The main component of the mulch film is PE, which accounts for about 99%. It can also produce ultra-thin mulch films.

[0024] (2) After years of use on various crops such as grain, cotton, and oil, it has been proven that its degradation control is good, it can keep the soil warm and moist, and the crop growth and yield are no different from ordinary mulch film.

[0025] (3) The non-starch type biodegradable polyethylene film prepared by the present invention does not contain toxic components, and the degradation products do not cause harm to soil or crops. The heavy metals in the additives are only iron. According to long-term data calculation, the change value of heavy metals during the degradation process is at the PPB level (trace level), and it remains non-toxic and harmless even after long-term application.

[0026] (4) The non-starch type biodegradable polyethylene film prepared by the present invention can be made into a mulch film with a thickness of up to 0.005 mm, and the covering cost is low. Attached Figure Description

[0027] Figure 1 The infrared spectrum of the non-starch-type biodegradable polyethylene film prepared according to the present invention;

[0028] Figure 2 The infrared spectrum of the non-starch-type biodegradable polyethylene film prepared in this invention after being covered in the field for 2 months;

[0029] Figure 3 The infrared spectrum of the non-starch biodegradable polyethylene film prepared in the application after being buried in soil for 3 months. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0031] Embodiment 1: The embodiment provides a non-starch biodegradable polyethylene film, which comprises the following raw materials in parts by weight: 10 parts of LDPE, 30 parts of LLDPE, 5 parts of HDPE, 0.01 part of acetyl ferrocene, 0.5 part of a biodegradation system, and 0.1 part of polyethylene wax.

[0032] The biodegradation system adopts stearic amide and calcium hydrogen phosphate, and the mass ratio of the two is 3:2.

[0033] The embodiment also provides a method for preparing the non-starch biodegradable polyethylene film by using a master batch method, which specifically comprises the following steps:

[0034] S1, acetyl ferrocene, a biodegradation system and polyethylene wax are weighed and placed in a stainless steel mixer, mixed at room temperature for 10 min until uniform, and a mixed material I is formed;

[0035] S2, 2 parts of LDPE are put into a high-speed stirrer, mixed material I obtained in step S1 is added, the high-speed stirrer is started, and 1% of anhydrous ethanol of the mass of mixed material I is sprayed at the same time, high-speed stirring is performed for 3 min, and a premix is obtained;

[0036] S3, the premix is sent into a double-screw extrusion granulator, the processing temperature is controlled to be 130 DEG C, and melting mixing, extrusion, cooling and granulation are performed, and a light biodegradable master batch is obtained;

[0037] S4, LLDPE, HDPE and 8 parts of LDPE are weighed and added into the light biodegradable master batch, and the two are dry-mixed in a mixer for 5 min until uniform, and a mixed material II is formed;

[0038] S5, put the mixture II into the hopper of the film blowing machine, melt and plasticize the material in the extruder, and set the parameters as follows: feeding section: 160 DEG C, compression section: 170 DEG C, homogenization section: 180 DEG C, head die: 175 DEG C, to obtain the molten material, then extrude the molten material vertically upward through the annular die to form a tubular blank, inject compressed air into the tubular blank to blow it up, control the blow ratio to be 2, and pull the film through the traction roller, cool and shape the blown bubble tube through the cold air blown by the cooling air ring, and form a stable frost line;

[0039] S6, measure the thickness of the film online in real time using a micrometer, and strictly control the thickness error within ±1 micrometer, in the production workshop, randomly cut a film sample with an area of 1 m 2 , weigh the film sample on a balance, the weight of the prepared degradable mulch film with a nominal thickness of 0.008 mm is 7.1 g / m 2 , the weight of the prepared ultra-micro degradable mulch film with a nominal thickness of 0.005 mm is 4.6 g / m 2 , and a non-starch biodegradable polyethylene film product is obtained.

[0040] Example 2: A non-starch biodegradable polyethylene film is provided, which comprises the following raw materials by weight: 48 parts of LDPE, 40 parts of LLDPE, 10 parts of HDPE, 0.3 parts of cyclohexene-based ferrocene, 2 parts of a biodegradable system, and 2 parts of an oxidized polyethylene wax.

[0041] The biodegradable system uses erucamide and calcium hydrogen phosphate, and the mass ratio of the two is 3:2.

[0042] The example also provides a method for preparing a non-starch biodegradable polyethylene film using a master batch method, which specifically comprises the following steps:

[0043] S1, weigh the cyclohexene-based ferrocene, biodegradable system and oxidized polyethylene wax, and place them in a stainless steel mixer, mix at room temperature for 12 min, until the mixture is uniform, to form a mixture I;

[0044] S2, put 8 parts of LDPE into a high-speed mixer, add the mixture I obtained in step S1, start the high-speed mixer, and at the same time, spray 2% of the mass of the mixture I into the high-speed mixer, high-speed stirring for 5 min, to obtain a premix;

[0045] S3, send the premix into a double-screw extruder, control the processing temperature to be 150 DEG C, melt, mix, extrude, cool and pelletize to obtain a light biodegradable master batch;

[0046] S4, weigh LLDPE, HDPE and 40 parts of LDPE, add the photobiodegradable masterbatch, dry mix the two in a mixer for 8 minutes, mix uniformly to form mixture II;

[0047] S5, put mixture II into the hopper of the film blowing machine, melt and plasticize the material in the extruder, set the parameters as follows: feeding section: 165 DEG C, compression section: 175 DEG C, homogenization section: 185 DEG C, die head die orifice: 180 DEG C, obtain the molten material, then extrude the molten material vertically upward through the annular die to form a tubular parison, inject compressed air into the tubular parison to blow it up, control the blow-up ratio to be 2.5, pull the blown bubble tube into a film by the traction roller, cool and shape the blown bubble tube by the cold air blown by the cooling air ring to form a stable frost line;

[0048] S6, measure the thickness of the film online in real time using a micrometer, and strictly control the thickness error within ±1 micrometer, in the production workshop, randomly cut film samples with an area of 1 m 2 , weigh the film samples on a balance to obtain the biodegradable mulch film with a nominal thickness of 0.008 mm and a weight of 7.2 g / m 2 , and the ultra-micro biodegradable mulch film with a nominal thickness of 0.005 mm and a weight of 4.8 g / m 2 , to obtain the non-starch biodegradable polyethylene film product.

[0049] Example 3: The present example provides a non-starch type biodegradable polyethylene film, which comprises the following raw materials by weight: 60 parts of LDPE, 50 parts of LLDPE, 20 parts of HDPE, 0.8 parts of a photosensitive system, 4 parts of a biodegradable system, and 3 parts of polyethylene wax.

[0050] The photosensitive system is an organic iron compound, which is a mixture of cyclohexenyl ferrocene and acetylacetone iron, and the mass ratio of the two is 1:0.5.

[0051] The biodegradable system uses oleic acid amide and calcium hydrogen phosphate, and the mass ratio of the two is 3:2.

[0052] The present example also provides a method for preparing a non-starch type biodegradable polyethylene film by using a masterbatch method, which specifically comprises the following steps:

[0053] S1, weigh the photosensitive system, the biodegradable system and the polyethylene wax, and place them in a stainless steel mixer, mix at room temperature for 15 minutes until uniformly mixed to form mixture I;

[0054] S2, 10 parts of LDPE are put into a high-speed stirrer, the mixed material I obtained in step S1 is added, the high-speed stirrer is started, and 3% of anhydrous ethanol of the mass of the mixed material I is sprayed at the same time, high-speed stirring is carried out for 5 min, and a premix is obtained;

[0055] S3, the premix is sent into a double-screw extrusion granulator, the processing temperature is controlled to be 180 DEG C, and melting mixing, extrusion, cooling and granulation are carried out, and a photobiodegradable masterbatch is obtained;

[0056] S4, LLDPE, HDPE and 50 parts of LDPE are weighed, the photobiodegradable masterbatch is added, and the two are dry-mixed in a mixer for 10 min, uniformly mixed, and mixed material II is formed;

[0057] S5, the mixed material II is put into a film blowing machine hopper, the material is melted and plasticized in an extruder, and the parameters are set as follows: the feeding section is 170 DEG C, the compression section is 180 DEG C, the homogenizing section is 190 DEG C, and the die head die port is 185 DEG C, the molten material is obtained, then the molten material is extruded vertically upwards through a ring die to form a tubular parison, compressed air is injected into the tubular parison to blow, the blow ratio is controlled to be 3, the film is drawn by a traction roller, and the bubble tube after blowing is cooled and shaped by the cold air blown by a cooling air ring to form a stable frost line;

[0058] S6, the film thickness is measured online in real time using a micrometer, and the thickness error is strictly controlled within the range of ±1 microns, in a production workshop, film samples with an area of 1 m 2 are randomly cut and weighed on a balance, a degradable mulch film with a nominal thickness of 0.008 mm is prepared, the weight is 7.3 g / m 2 , an ultrathin degradable mulch film with a nominal thickness of 0.005 mm is prepared, the weight is 5.0 g / m 2 , and a non-starch biodegradable polyethylene film is obtained.

[0059] Embodiment 4: The embodiment provides a non-starch biodegradable polyethylene film, which comprises the following raw materials in parts by weight: 48 parts of LDPE, 40 parts of LLDPE, 10 parts of HDPE, 0.3 parts of cyclohexene-based ferrocene, 2 parts of a biodegradable system, and 2 parts of an oxidized polyethylene wax.

[0060] The biodegradable system adopts stearic amide and calcium hydrogen phosphate, and the mass ratio of the two is 3:2.

[0061] The application also provides a method for preparing a non-starch biodegradable polyethylene film by using a direct method, which comprises the following steps:

[0062] Y1, the cyclohexenyl ferrocene, biodegradable system and oxidized polyethylene wax are weighed, all the solid powdery additives are placed in a stainless steel mixer, mixed at room temperature for 15 min until uniform, and a mixture III is formed;

[0063] Y2, in a high-speed mixer, LDPE, LLDPE and HDPE are weighed, and the mixture III prepared in step Y1 is added, the machine is started, and 2% of the mass of the mixture III of acetone is sprayed at the same time, high-speed stirring is carried out for 5 min, and after floating on the surface of the resin, the material is discharged to obtain a direct film-forming mixture;

[0064] Y3, the direct film-forming mixture obtained in step Y2 is directly put into a film blowing machine hopper, the material is melt-plasticized in the extruder, and the parameters are set as follows: feeding section: 165 ℃, compression section: 175 ℃, homogenization section: 185 ℃, die head: 180 ℃, to obtain a melt material, then the melt material is extruded vertically upward through an annular die to form a tubular parison, compressed air is injected into the tubular parison to blow, the blow ratio is controlled to be 2.5, the film is drawn by a traction roller, the bubble tube after blowing is cooled and shaped by the cold air blown by a cooling air ring to form a stable frost line, the film thickness is measured online in real time using a micrometer, and the thickness error is strictly controlled within ±1 micrometer, in the production workshop, a film sample with an area of 1 m 2 is randomly cut and weighed on a balance to prepare a biodegradable mulch film with a nominal thickness of 0.008 mm, and the weight is 7.2 g / m 2 , a super-micro biodegradable mulch film with a nominal thickness of 0.005 mm is prepared, and the weight is 4.8 g / m 2 , and a non-starch biodegradable polyethylene film is obtained.

[0065] In Comparative Example 1, a general polyethylene film is used to prepare a general PE mulch film with a thickness of 0.08 mm.

[0066] In Comparative Example 2, a starch-based biodegradable polyethylene film is used to prepare a starch-based biodegradable mulch film with a thickness of 0.08 mm.

[0067] Experimental Example:

[0068] 1. Mechanical strength: The mechanical strength of the non-starch biodegradable polyethylene film prepared by the present application was determined according to the national standards GB / T 1040.3-2006 "Determination of tensile properties of plastics" and GB / T3830-1994 "Peel test method for soft composite plastic materials". The non-starch biodegradable polyethylene film prepared by the present application examples 1-4 and comparative examples 1-2 was used as the film sample; wherein two thickness specifications (0.008 mm and 0.005 mm) of film were prepared for each example; accordingly, examples 1-1, 2-1, 3-1 and 4-1 in the table correspond to the film with a thickness of 0.008 mm prepared by example 1-4, and examples 1-2, 2-2, 3-2 and 4-2 correspond to the film with a thickness of 0.005 mm prepared by example 1-4. The test steps are as follows: cut the film sample into standard dumbbell-shaped or rectangular samples; use a universal material testing machine to test at room temperature (23°C); set appropriate clamp spacing and tensile speed (usually 500 mm / min) until the sample breaks. Record the tensile strength (MPa) and elongation at break (%) of the sample in the longitudinal and transverse directions, and calculate the right-angle breaking strength (N / cm) as needed. The results are recorded in Table 1.

[0069] Table 1: Mechanical strength of non-starch biodegradable polyethylene film

[0070]

[0071] From the data in Table 1, it can be seen that the mechanical strength of the non-starch biodegradable polyethylene film prepared by the present application with different thicknesses all meets the national standard of ordinary mulch film, and the present application successfully overcomes the defect of poor mechanical properties of traditional starch-based film while imparting biodegradability to the polyethylene film, meeting the use requirements.

[0072] 2. Biodegradability: The non-starch biodegradable polyethylene film prepared by the present application examples 1-4 and comparative examples 1-2 was used as the film sample, the film sample was cut into pieces, 10.0 mg was weighed as the only carbon source, and was placed in a test tube containing a carbon-free liquid medium. After sterilization, a specific pure bacterial strain (such as Bacillus subtilis, Pseudomonas aeruginosa, etc.) was inoculated. Sealed culture (30°C, 40 days), periodically determine the amount of CO2 released using a gas chromatograph. Calculate the carbon content in CO2 (CO2-C, μg) to represent the degradation ability of microorganisms to the film.

[0073] Table 2: Degradation ability of microorganisms to non-starch biodegradable polyethylene film (CO2-C μg / 40d)

[0074]

[0075] As can be seen from Table 2, the bacteria and fungi capable of growing on the surface of the test film have the degradation ability to the film in accordance with the length of growth on the film. After pure bacterial culture for 40 days with 10 mg of test film as a group of unique carbon source, the amount of CO2 released by each group of test substance was determined and the C content was calculated, and the highest value reached about 600 ug, which exceeded the C content value in the auxiliary agent in the film. This indicates that the C in PE has been utilized by microorganisms, and it is worth noting that the microbial growth of Comparative Example 2 is higher than that of the inventive examples, but its degradation relies on direct microbial decomposition of starch, which has inherent defects such as poor mechanical strength, easy residual PE fragments after starch degradation; while the inventive examples are non-starch type systems, which rely on the synergistic effect of photo-oxidation and biodegradation, and can achieve complete degradation of PE body in the long term without residue. The present application gives biodegradability while taking into account good mechanical strength, overcoming the application defects of traditional starch-based films, indicating that the non-starch type biodegradable polyethylene film prepared by the present application has good biodegradability.

[0076] 3. Buried degradation: the non-starch type biodegradable polyethylene film prepared by the inventive examples 1-4 and comparative examples 1-2 is used as a film sample, and the film sample is buried in the soil in different regions (such as Liaoning brown soil, Sichuan farmland soil). The sample is taken out at different time points (such as 2.5 months, 5 months, 11 months). After cleaning and drying, the change of the viscosity average molecular weight is determined.

[0077] Table 3: Change of number average molecular weight

[0078]

[0079] As can be seen from Table 3, in the Feili medium soil in the northern high latitude area, the molecular weight of the buried residual film decreased by more than 40% in just one year. From the beginning of film mulching to the soil thawing the next year, the molecular weight of the buried soil decreased by about 30% in the first five months, and by about 10% in the last six months, which seems to slow down the degradation rate, but careful analysis shows that the buried soil film is in the frozen soil layer for nearly five months, not only the microbial activity is inhibited, but also the speed of various degradation chemical reactions of the film will be inhibited, therefore, the decrease of the molecular weight of the buried residual film slows down, which is caused by the low temperature of the frozen soil layer, and is not caused by the degradation stagnation of the buried residual film. With the rising of temperature in winter and spring, the microbial population activity in the soil will be enhanced, and the degradation reaction speed occurring in the residual film will also be accelerated, and the decrease of the molecular weight of PE will definitely be faster and faster, and will not stop.

[0080] Figure 1 The infrared spectrum of the non-starch type biodegradable polyethylene film prepared by the present application, Figure 2 The infrared spectrum after 2 months of field mulching, Figure 3The infrared spectrum after being buried in soil for 3 months. Figure 1 The original film spectrum only presents the characteristic absorption peaks of polyethylene molecules, without signals of additional oxygen-containing functional groups, indicating that the molecular chain structure is stable in the initial state of the film; from the spectrum Figure 2 It can be seen that after the non-starch biodegradable polyethylene film is covered in the field, a large number of complex absorption peaks appear in the functional group region of 4000-1300 cm -1 of the infrared spectrum, which are carbonyl, hydroxyl, carboxyl and other oxygen-containing groups and double bonds, indicating that the polyethylene has been oxidized, which will inevitably lead to the rupture and decomposition of the long chain of polyethylene, and eventually become a carbon source for microorganisms. After being buried in soil for 3 months, the light degradation effect basically stops due to the lack of light in the soil environment, and Figure 3 from the spectrum, new functional groups also appear in the fingerprint region below 1300 cm -1 , which indicates that the polyethylene molecular chain continues to break and decompose under the metabolic action of soil microorganisms, further generating small molecular oxygen-containing compounds, fully proving that the film can continue to decompose through the biodegradation path under the condition of no light, realizing the coordinated connection of photodegradation and biodegradation.

[0081] In summary, the raw material system of the present application does not add starch, uses polyethylene resin as the base material, matches with a specific photosensitive system, a biodegradation system and a dispersing agent, and realizes the balance of degradation performance and use performance through scientific compounding. The preparation process includes two independent feasible processes of master batch method and direct method, the master batch method can flexibly adapt to different grades of polyethylene raw materials and is suitable for large-scale multi-variety production; the direct method omits the granulation link, the process is more simple and efficient, and meets the rapid production demand. Both processes use float dyeing method to ensure uniform dispersion of the auxiliary agent, cooperate with unified film blowing parameters and strict thickness control to ensure product quality stability. The prepared film has mechanical strength meeting the application requirements, can realize the synergistic effect of photodegradation and biodegradation, can gradually degrade after being used in the field, avoids residual pollution of soil, and takes into account practicality and environmental protection, providing a reliable scheme for green application of polyethylene film.

[0082] The above describes the present application and its embodiments, which are not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the present application, and the actual application is not limited thereto. In summary, if a person skilled in the art is inspired thereby, without departing from the purpose of the present application, similar modes and embodiments can be designed without creative design, which shall belong to the protection scope of the present application.

Claims

1. A non-starch biodegradable polyethylene film, characterized by, The raw materials include the following weight parts: 10-60 parts of LDPE, 30-50 parts of LLDPE, 0-20 parts of HDPE, 0.01-0.8 parts of a photosensitive system, 0.5-4 parts of a biodegradable system, and 0.1-3 parts of a dispersing agent; The photosensitive system is an organic iron compound selected from one or more of acetylferrocene, cyclohexenylferrocene, n-octylferrocene, butyl butyrate ferrocene, acetylacetone iron, and benzoyl ferrocene; The biodegradable system includes an organic amide compound and calcium hydrogen phosphate; The organic amide compound is selected from one of stearic amide, erucic amide, and oleic amide; The dispersing agent is at least one of polyethylene wax and oxidized polyethylene wax.

2. The non-starch type biodegradable polyethylene film as claimed in claim 1, wherein, The non-starch biodegradable polyethylene film is prepared by a master batch method or a direct method.

3. A process for the preparation of a non-starch biodegradable polyethylene film according to claim 2, characterized in that, The non-starch biodegradable polyethylene film is prepared by a master batch method, specifically including the following steps: S1, weigh the photosensitive system, the biodegradable system, and the dispersing agent, and mix them uniformly at room temperature to form a mixed material I; S2, add the mixed material I obtained in step S1 to part of the LDPE, and stir at high speed to obtain a premix; S3, melt mix, extrude, cool, and pelletize the premix to obtain a light biodegradable master batch; S4, dry mix the LLDPE, the HDPE, and the remaining part of the LDPE with the light biodegradable master batch prepared in step S3 to form a mixed material II; S5, blow film by melt plasticizing, blowing, and cooling and setting the mixed material II to form a stable frost line; S6, measure the thickness of the film online to obtain the non-starch biodegradable polyethylene film.

4. The process for the preparation of a non-starch type biodegradable polyethylene film as claimed in claim 3, wherein, In step S5, the temperature parameters of the melt plasticizing are set as follows: the feeding section: 160-170 ℃, the compression section: 170-180 ℃, the homogenization section: 180-190 ℃, and the die head: 175-185 ℃.

5. The process for the preparation of non-starch type biodegradable polyethylene film as claimed in claim 3, wherein, In step S6, for the degradable mulch film with a nominal thickness of 0.008 mm, the weight is controlled in the range of 7.0-7.5 g / m 2 For the ultra-micro degradable mulch film with a nominal thickness of 0.005 mm, the weight is controlled in the range of 4.5-5.0 g / m 2 .

6. A process for the preparation of a non-starch type biodegradable polyethylene film according to claim 2, characterized in that, The non-starch biodegradable polyethylene film is prepared by a direct method, including the following steps: Y1, weigh the photosensitive system, the biodegradable system, and the dispersing agent, and mix them to form a mixed material III; Y2, weigh the LDPE, the LLDPE, and the HDPE, add the mixed material III prepared in step Y1 thereto, spray anhydrous ethanol, and stir at high speed to obtain a direct film-out mixed material; Y3, directly blow film with the direct film-out mixed material obtained in step Y2 to obtain the non-starch biodegradable polyethylene film.

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